by B.B. Pelletier
Good morning, everyone. Although I didn’t respond to most of you yesterday, I did read what you said. I’m in the process of asking for some more permanent guest bloggers, and we’re looking into the “Recent Comments” widget. At this point we think we have to write the code ourselves. Does anyone know of a similar widget that already exists?
I’m sorry if I sounded like a whiner yesterday, and I hope I didn’t scare my old Airgun Letter readers into thinking I was abandoning them again. I assure you, nothing of the kind is in the works.
But there IS something very exciting in the works, and I will tell you about it in this blog a week from today. On that day, Thursday, Jan. 15th, which is the first day of the SHOT Show, I will be attending the Airgun breakfast that Pyramyd AIR is hosting in Orlando. A huge announcement will be made at the breakfast at around 7:45 a.m. Eastern time. I am scheduling that day’s blog to publish at the same time, rather than the normal 6:30 Eastern time it now publishes. You’ll hear the news in the blog at about the same time it is announced to the airgun industry. I will say no more about this until that morning.
Now, let’s get to today’s report.
Let me begin by saying that I do not know exactly how fast an airgun can shoot. But I have done some testing and I have observed some things, so I’m at least qualified to talk on this subject from my personal experience.
Why am I waffling so? Because this topic is a hot button in the airgun community. There are endless discussions on forums, and many “experts” present their data and formulae to prove this or that point. The ones I enjoy most are the guys who admit that they don’t own a chronograph or even have access to one, but they offer scientific “proof” that it’s physically impossible for an airgun pellet to exceed the sound barrier when powered by air only. They may actually have a minor point, since the Cardews (The Airgun From Trigger to Target) proved that all spring-piston guns over a certain velocity diesel with every shot, but that doesn’t take pneumatics into account. I plan to.
I’m going to share what I know for sure, and you guys can take it from there. I’ll also write a short article on this subject for the Pyramyd AIR website and accompany it with a long video of Dennis Quackenbush and me doing some testing at the 2008 LASSO big bore shoot.
I’ll give all the support I have for what I tell you, but I’m not going to postulate why things are the way they are. My science background is not strong enough to support that discussion [Jane Hansen–Are you reading?], so I’ll just share the actual data I’ve seen and collected.
This discussion probably started back in the early 1970s, when the 800 f.p.s. “barrier” was first broken. Maybe it was broken before then, but I know for certain that the long-stroke FWB 124 in .177 caliber could reliably exceed 800 f.p.s. with some light pellets, and the airgun community treated it as a BIG DEAL.
Yawn.
No doubt Vince is wondering if I’ve lost my mind by rambling on about 800 f.p.s., but the 1970s were a time when that was considered big stuff. And then 1,000 f.p.s. was exceeded in the early 1980s, and a few years later Diana topped 1,100 f.p.s. with their new sidelevers. Finally, Ivan Hancock built the Venom Mach I, a breakbarrel spring rifle that exceeded the speed of sound…and everything was up to date in Kansas City.
For a decade, the goal for a powerful smallbore airgun was to exceed 1,100 f.p.s. and go supersonic, if possible. Before you tell me, I know the sound barrier can also be below 1,100 f.p.s., but it was always held separate from the chronograph readings, so I’m reporting it that way.
In 1999, Gamo decided we hadn’t gone far enough, and they brought out the Hunter Hurricane 1250. That’s right, it was supposed to shoot 1,250 f.p.s. Well, as I was writing The Airgun Letter at the time, I decided to test it. Who did Gamo think they were, making a claim like that?
The thing is, their rifle REALLY DID shoot that fast. Or at least the one I tested did. Those where the days before we had the lightweight trick pellets, so they had to get there with an RWS Hobby, which weighed 6.9 grains back then. I saw several shots from my test rifle go faster than 1,250 f.p.s., and the fastest one went 1,254 f.p.s. The velocity race went into overdrive.
In 2006, Gamo transformed the 1250 Hurricane into the Hunter Extreme, and, by virtue of the new Raptor PBA pellet, they now advertised it at 1,600 f.p.s. And right there, history was made.
That was the first hyper-velocity pellet rifle I saw that failed to live up to the hype. I tested it for you in this blog.
Stop right there!
In my test, the Hunter Extreme went up to 1,395 f.p.s. Not bad at all, but a far cry from 1,600 f.p.s. To add insult to injury, Gamo now laser-engraves the expected velocity on the compression tube of the rifle, and there it says to expect 1,650 f.p.s. I got 1,395 f.p.s. I asked you readers to give me your velocities and nobody did. Other airgunners I contacted told me their Hunter Extremes went as fast as 1,425 f.p.s. Again, not too shabby, but not 1,600 f.p.s., either.
Gamo ENGRAVES the expected velocity on the steel compression cylinder of the Hunter Extreme. In all my testing and correspondence with other Hunter Extreme owners, this number has never been approached, except when the rifle detonates some fuel.
This is the average velocity I saw from the Hunter Extreme shooting Gamo Raptor PBA pellets. The top speed I recorded was 1,395 f.p.s.
Just as I was recoiling from that test, Benjamin brought out the Super Streak, which they advertise to shoot up to 1,500 f.p.s. That threw me back into the testing mode again, and I came up with a top speed of 1,323 f.p.s. with Raptors. Nowhere close to 1,500 f.p.s. In fairness, the Crosman Silver Eagle pellet line was new about the same time, and I didn’t try them with this rifle. The hollowpoint is only 4.8 grains and has been beating the Raptor in velocity tests, so it might have boosted the number a little. But not enough.
While I was still on the ropes from the Super Streak, RWS Diana brought out the 460 Magnum–a rifle that was advertised to reach 1,200 f.p.s. in .177 (though one airgun internet retailer has it listed at 1,350 f.p.s. for some reason). Have you noticed anything strange yet?
What’s strange about this trend?
What’s strange is that the top velocities advertised are FALLING, rather than increasing. Gamo still advertises 1,600 f.p.s., but Benjamin, who came out later than the Hunter Extreme says their hyper-velocity gun is 100 f.p.s. LESS. And now the RWS Diana 460 Magnum drops another 300 f.p.s in their claim. And it’s an important 300 f.p.s., because some airguns really can go 1,200 f.p.s. I actually got up to 1,155 f.p.s. from the test 460 shooting Raptors. I point this out without comment.
Then why do they advertise 1,600 f.p.s.?
They advertise it because the rifles can do it. With a little oil down the transfer port, the Hunter Extreme can go faster than 1,600 f.p.s. It takes a small explosion to go that fast, or at least in my experience there has never been a test rifle that went that fast without a violent detonation. And therein lie several problems.
Problem 1 – blown seals
Back in prehistoric airgun times, Weihrauch had the Barakuda EL-54 ether-injected breakbarrel rifle that was built to propel a 15.3-grain .22 caliber round lead ball to 1,000 f.p.s. H&N even made a special 21-grain lead diabolo pellet for the rifle they called the Baracuda. Later, Beeman called it the Kodiak. Read about that rifle here.
The trouble was that with all the explosions, the Barakuda rifles couldn’t keep their leather seals from blowing. It was an idea ahead of its time.
Problem 2 – it’s not an airgun
The definition of an airgun varies by country. The U.S. is pretty open as far as power and velocity go, but a firearm cannot be an airgun.
Who said anything about a firearm?
Well, to paraphrase the legal definition of a firearm, it’s “any device that propels a projectile or projectiles by means of an explosion.”
Yes, certain springers achieve super-high velocities, but to do so seems to take an explosion. If that’s true, we’re not talking about airguns anymore.
The gun that fired the .22 Daisy VL caseless cartridge used a spring-piston powerplant to heat the air that ignited the compound on the base of the bullet. That compound then burned rapidly enough to seem like an explosion. Therefore, the Daisy VL system was considered a firearm
Okay, there’s some food for thought. In the next part, I’ll tell you what Dennis Quackenbush decided to do about it, and I’ll also share my experience of the fastest true airgun shot I ever witnessed.
Hi BB,
I am a gun blogger myself. I am willing to help with any custom programming for no cost.
I love your blog and would be more than happy to help.
Interesting blog. I can’t wait to read the next one. I am also curious to learn if it is possible to maintain accuracy with such high velocities. From what I currently understand, this is not the case. Maybe a new barrel or pellet design could solve that problem and open up some longer ranges and larger game to airgunning.
This question isn’t for B.B. (although if he has an answer and want to chime in…) This is for B.B.’s readers. If anyone out there has a Beeman RX-1 in .177 or .22 would you please give me your Chrony numbers with Beeman 10.6 Gr. Kodiaks and/or 21.1 Gr. Kodiaks. Thank you in advance from SavageSam
Steve,
Nice blog and very nice offer to B.B.
Hello Everyone,
Re: Book report
I was interested in broadening my knowledge of airguns (especially springers) velocity, accuracy, tuning, hold, affect of lubrication, break in periods, tips on shooting technique, etc.
For anyone else that has the same desire to maximize the potential that lies in your gun, your shooting ability and unlock the "mysteries" of all the variables that should/could be taken into account I would recommend two books:
1-Number one has to be The Beeman R1 written by Tom Gaylord. Very well written and an easy read. Don't be fooled by the title. Although the R1 is the airgun used to navigate you through the numerous tested options that exist to maximize your enjoyment and potential of an R1, it easily translates to all springers. If you only want to read one book to become a more informed owner/shooter/tuner of a spring gun this is the book.
2-The Airgun from Trigger to Target written by G.V. Cardew & G.M Cardew. Relevant book for airgunners that drills even deeper into the performance of airguns. Although a layman can muddle through this read (I did), it's only going to be enjoyed by the scientist in you. This is the book that will disprove current myths like lock time. It also opens your eyes to factors that must be considered like internal lubricants being used for fuel in the shot cycle.
Since many of us live in climates that this time of year are more conducive to curling up with a book by the fireplace than shooting outdoors I thought I'd throw these out.
kevin
Volvo,
Thanks for the link to the latest opinions on the AA S410 vs. FX Whisper.
Very similar to the previous posts (some that you initiated). Sure seems like the guns are very similar. Each owner is passionate about the gun he owns but I put more stock into those owners that have shot both guns. Seems that I agonized over this decision as much as you did. Narrowed by selection down to 5 guns including the new BSA and older HW100. Weight, adjustable power, ft lbs, broad flat spot on the power curve, fit and finish were high on my list of criteria.
Although I made my choice (I think you already know what it was) I still don’t have the gun. These are hard to find! Hopefully only a week away. We’ll see.
Watch out pcp world another idiot will be walking through the door!
kevin
B.B.,
I’ll speak for everyone. Nobody thought you were whining yesterday. We all recognize how much effort you put into this wonderful blog, and we are awed by your dedication.
From all of us
B.B. & All,
I'm amazed at how easy the American market gets caught up in speed. Without looking at what comes with it.. loss of accuracy..
In my opinion, the best speed is between 800 & 900 fps. Then choose a gun that shoots the right weight pellet for the job.
The reason one might think they want more speed, is probably they think more speed means more power or "foot pounds" at the target… Or at least I hope that's why…
I would much rather have accuracy going 800fps with a pellet weighing enough to know down the target, whether it's a steel one or a live one..
Just my half cent worth..
Of course, most manufactures in this race, are just interested in sales volume, not quality, or "getting the job done" for the customer..
Wayne,
Ashland Air Rifle Range
Dr. G.
Wow, I can hardly wait for the details of your airsoft extravaganza.
Welp, here it is: How I Shot Myself With An Airsoft Pistol
Preamble:
Yesterday a box of goodies arrived from PA. I had ordered a Crosman 2250B to replace my favorite SSP 250 with blown seal. Since shipping is very expensive from PA here to Maui, I threw in a couple extras, including a GBB airsoft version of the PPK/S, since I already own two of the CO2 versions (black and tuxedo). I decided to do a short test of the PPK/S first.
The Point:
I got 2 1/2 mags-worth of BBs from a fill. I decided, HEY! Why not try filling the mag with propane while it's in the gun? So I wedged the pistol between my legs and inserted the propane probe. BLAM! The pistol went off, shooting me in the left inner thigh (unfortunately I was wearing shorts). I didn't yelp, although I believe I had every right to…I was just so astonished. The BB didn't break the skin but left a blood blister and a stinging reminder of why one does not fill a mag with gas propellant while it's still in the pistol.
Of course my Inner Scientist had to repeat this, just to see if it was an anomaly. Setting the pistol /very carefully/ with its bbl pointing somewhere safe (ie. NOT aimed at any part of my body), I re-inserted the propane bottle. It did indeed activate the pistol's action. Satisfied, I happily gave up this line of experimentation.
Conclusion:
So that's it, Boys and Girls. Do not try this at home unless you're into some rare form of airsoft S & M.
Interesting Side-Note:
[It was my 26-year old, adopted daughter's birthday last night. She invited some of her S & M friends. Very sweet people…not a trace of a whip or handcuffs anywhere…. We all fell asleep watching "Harold and Maude".]
-Joe B.
Hey EJ-
Lloyd actually mentioned the index sometime during the time I was typing my post. For those times when a search isn’t productive an index would be a way to get you in the ballpark. I’ve thought about it some more and it would probalby be best to do the index by year as it might be too hard to update otherwise.
One problem though might be the fact that Tom illustrates his teachings in such a way that cross indexing could be a real challenge. For example, I was trying to further my nephew’s interest in the shooting sports and remembered a couple of great sharpshooting anecdotes that Tom had included in previous posts. One of the stories, about Billy Dixon, was buried in a post about “Calibers and Range”(10/09/2006). The other was about a Union captain’s 1 mile sniper shot hidden in the post “Shooting from a Vice”(06/21/2007). I couldn’t remember Billy Dixon’s name until I found the post so I couldn’t find either by trying a search(maybe some out there could however). I just waded in until I found them but the point is they were stories used to illustrate the main blog entry. Tom has such a broad knowledge that a detailed index could be a real challenge. I’m thinking it would have to be a general index instead of a truly exhaustive one. Do you categorize the blogs about the Zimmerstutzen as “Collectibles” or “History”? Maybe both! If we could come up with a framework for the index then it would be just a question of putting things in the right slot. There just seems to be a lot of potential gain to having an index. The pain comes from doing the archives. If it got going soon, 2009 would be just a question of building it as it goes.
Gavin
PS- Tom, I posted this today since there were so many comments yesterday that I was afraid it would get lost. If this idea gathers any momentum, would you be adverse to be contacted using your contact from Airgunwriter? I promise to make the email brief if you think this idea has any merit. I’m also going to post this on yesterday’s blog in case EJ looks there. Thanks!
RE: Pellet faster than speed of sound
As a chemist I feel qualified to answer the notion.
The speed of sound is dictated by how fast the air molecules are moving. In an ideal gas the speed of sound depends only on temperature not on pressure. So the naive interpretation would be that the speed of sound is a constant dependent only on temperature, and hence a pressurized gas can’t push a pellet faster than the speed of sound.
If fact when the pressure is released into the breech of a gun there is high pressure on one side of the pellet and atmospheric pressure on the other. When the pellet starts moving the gas molecules are not at equilibrium. That is to say that random motion is not equal in all directions. There is a preference for the molecules to be moving down the barrel instead of either of the two directions perpendicular to the barrel. So the absolute limit would in fact be something between 1 and 3 times the speed of sound. Think of a frictionless, virtually massless pellet whizzing down the barrel.
For a pneumatic gun, the gas will actually cool as it expands, thus reducing the energy available to power the pellet.
For a springer, the gas will actually be heated as it is compressed then cool as it flows through the transfer port to a region of less pressure. This would further complicate an exact mathematical simulation.
Numb3ers fan,
Herb
Steve,
Thank you for your generous offer. I forwarded it to our webmaster for approval. I really hope he says yes, because we have not found any existing widgets that do what I would like to have done.
B.B.
I’m pretty sure that I made a comment, a few months ago, about airgun manufacturers forcing their rifles to detonate in order to achieve higher velocities for advertisements.
This also reminds me of how firearm manufacturers use hand loads to test their rifles for accuracy. Ammo manufacturers also use specialized test barrels to test their ammo.
This post also reminded me of a paintball gun that came out a few years ago. The Tippmann C3 is a paintball marker that is powered by propane. It is technically a firearm, but I have never heard of any licensing issues with one. You can even purchase them online and have them shipped directly to your house.
RE: Speed of pellet vs shooting precision
Wayne!
Who cares about precision !?!
When I shoot squirrels I have discovered that I don’t have to hit them. They are so intimidated by the sonic crack of the PBA pellets that they just die of fright.
😉
Herb
Herb,
It has been documented that the .50 BMG round does not have to hit its target to be lethal. If the bullet passes within a foot of your head, at relatively short range, the pressure wave from the bullet is powerful enough to liquefy your brain.
Perhaps this is what Gamo was trying to do when they developed the PBA pellet.
Gavin,
Contact away.
B.B.
BB
How about you cutting down posting to once in two days. I do hope that will give you time to rest.
Manish
Mumbai
India
RE: Widget for Blog
I noticed the “Powered by Blogger” logo on the blog.
Don’t think that it will be easy, if even possible, to create a widget. I run a website for a professional group. My impression is that the Blog is actually a utility on a Google server on which Pyramid Air has no programming capability.
My semi-educated guess is that BB created the blog on Google so that he would own it. Pyramid Air just has a links from their site to the Google addresses of the blog.
The way to do this would be for BB to have his own website. Add a blog tool. Customize the blog tool (or roll your own) to conform to specifications required.
One way to do it would be to have different kinds of entries in three different tables of a database. The blog entries are one-a-day in a table as BB does now. The comments are dated in a second table. The third table is an association between blog and comments. The initial association is set to the blog for which the comment is entered.
After a month when the blog is archived, the index is updated and the comments are “re-keyed” to the blog(s) for which they are pertinent.
All in all having such a blog would be more editorial work. Such a blog would be interesting as something between a wiki and a blog. BB could control content, and his “associate editors” would do indexing and keying of comments.
Herb
Manish and everyone,
Thank you for your concern. Just by ignoring many comments I would normally respond to, I have regained a lot of time.
This blog will continue pretty much as it has been for the foreseeable future. Some readers are already contacting me to offer special help, which I think will really work well.
Thank you,
B.B.
mechredd:
RE: PBA pellet
You’re right about pressure wave of large bullets, but PBA pellet was created primarily to go after speed bragging rights.
I was pulling Wyane’s right leg so hard that he is going to have to use a lift in his left shoe.
Herb
Re: Blog Index (my two cents)
Indexing and cross indexing and categorizing and cross categorizing will be a nightmare. I would be satisfied with just a list of blog titles with their creation date. Edith can build that in one day. She’s that good.
The search engine already in place on the blog page coupled with the “Find” option of my browser seems to work for me. True, I’d probably miss that question of whether the Dianna xx is better than the Moped II that’s buried in the Walther PPK blog replies but that just adds credibility to the idea of a forum.
$0.01 down one to go.
-Chuck
Re: Blog Index
Well, I don’t disagree that the cross-indexing is work.
I disagree that a list of blog titles is sufficient.
I disagree that off-topic comments in a particular blog are superfluous.
The problem is that the overall interaction of this community isn’t truly a blog, a wiki, or a forum. It is something in between all of those tools.
I’ll expand my idea above to also include another table for forum topics. For instance I don’t think that BB has blogged on the “Absolute speed limit for a pellet.” So the discussion about that idea could be moved to a forum topic.
You can search quite easily for a phrase in any of BB blogs using Google. The problem is that when you open that hit it shows the blog for that day and all comments for that day. Trying to follow a particular train of thought while looking at all of the stuff for that day is difficult.
Herb
Herb,
Let go of my leg!… how can I shoot straight at 5,000fps, with the dog wanting to be fed, and you hanging on my leg.. I’ve got to get that fly on the wall, my fly swatter has a broken handle.. and the daisy 499, that Vince souped up, is my only chance… I just hope it doesn’t drop to 4,999 or I might miss…
Wayne
Herb,
I know that the PBA was created for velocity bragging rights. It seams like the PBA was Gamo’s attempt at making a faster pellet rifle without actually making a faster pellet rifle. Unfortunately, people get velocity confused with power, and all the power in the world wont save you if you can’t hit your target.
Well… Maybe it can considering pressure waves and all. 🙂
Honestly, I feel that the high price, poor accuracy, lack of downrange energy, and loud noise, vastly out weigh the flatter trajectory of the Raptor pellet.
I just wish that airgun mfgs. would list the weights of pellets used with their testing to show how they come up with these FALSE velocities because 99% of all hunters will NEVER use a lightweight trick pellet for hunting purposes. Should be a requirement to show how Gamo comes up with false claims of 1650 fps. when nobody ahs even come close to those numbers.
mechredd,
Totally agree.
But it is called marketing. We have a federal bureau (FDA) to regulate drug claims. But note how many infomercials are on TV selling snake oil remedies for bowel cleansers and such.
Part of problem is that marketing is more concerned with finding a new sucker (ie PT Barnum style) than developing a real relationship.
Gamo isn’t going to use “real” pellets to advertise their rifles because they don’t want to give up the velocity “edge” that they have.
No doubt there are a lot of nit wits that are thinking “Rifle kicks like mule, and pellet goes CRACK. Me bigg’em hunter.”
😉
Herb
Good afternoon B.B. the word magnum coupled with hyper velocity is what the marketing folks in our industry think sells their air rifles. Look at all the guys in the East shooting 300 Winchester Magnums at while tails, just in case they get that 400 yard shot.
Then it takes awhile for them to hopefully realize that they need to be shooting around 900fps, go talk to them Wayne, gotta stay below the speed of sound because of stability issues.
They have walked on to our range, but will they stay? That is why this blog is so important to our sport.
I started with an S&C and don't know much about computers, but we all can help by answering questions, giving advice, sharing experiences, etc.
Herb, if I understood Cardew right, the compressed air flowing through the transfer port continues to heat up in the transfer port, and does not start to cool down until it gets out of the transfer port. A white light was witnessed by Cardew in the transfer port, which was thought to be some type of combustion. Cardew actually installed a little perspex clear window in a springer’s transfer port.
cant find my post I sent from earlier so here is a repost :forgive me if dub but cant find it 🙂
False velocity claims doubt it just markeing bs. They are not claiming the projectile is a CP or hobby etc. They are more than likely stating the MAX that is possible with a gun they built. That would be a felt cleaning pellet and a newly lubed gun with a bit of smoke in a 200mph lambo:)
Herb,
Your points are well taken. I apologize for making you think I was implying superfluous replies. I think my intent was to sell the “forum” model where everyone stays on topic.
I think what B.B. has here is more like a blog followed by instant messaging and I love it. I know it has paid off for me the times that I needed it. And I don’t stay on topic, either. I don’t want this format to end, but he needs help. Well, I guess we’ve all agreed on that. Now I’m being redundant.
Your comment about going to the blog and then having to wade through all the replies to find the info you need is true with the newer blogs. The earlier blogs had only one topic per “page” and the replies followed them on the same page. I could then use my browser to “FIND” again on the same words I used to get to the blog and that would take me to the desired reply. I could follow that up with the “SEARCH AGAIN” option. I see that that isn’t true with the new blogs, at least with the browser I’m using. There is no way to search within the reply section. That would be nice to have back.
-Chuck
And I keep forgetting to check that email follow-up box.
-C
Chuck,
Let’s get our terminology consistent. The blog for each day has two sections. The blog “article” and the “comments.” You can search both with Google as I pointed out a few days ago.
(1) Type whatever you want to search for in “Search” field of blog page being displayed.
(2) On resulting search screen from Google replace “blogurl:” with “site:”
(3) Click “Search the Web” button (which is restricted to webpages at/blog// and below.
Herb
B.B.,
I did a quickie test a while back to see how fast the trick PBA pellets lost velocity. Compared it to a Beeman Kodiak.
Gamo Shadow1000
at 1 yard
Gamo PBA 5.0gn 1134fps, 14.3fpe
Kodiak 10.6gn 786fps, 14.5fpe
at 7 yds
Gamo PBA 5.0gn 982fps, 10.7fpe
Kodiak 10.6gn 756fps, 13.5fpe
So, in 6 yds, the PBA lost 25% of its energy and the Kodiak lost 7%.
Pretty telling.
Lloyd
Herb,
Thanks for the info. I had never used the “site:” parameter before. It is handy isn’t it?
Also, If we are standardizing terminology. I think we are both only partially correct. According to the box on the right hand side of the “blog” they are called “Posts”. However, you are correct in calling the comments “comments” whereas I called them “replies”. (pretty soon one of us is going to go: neener, neener.)
-C
Oh, one other thing Herb,
Once you get to the correct post how do you do a search within the comments window. I’ve tried both Firefox and Internet Explorer and can’t find a way to search them.
-Chuck
RE: Cardew & transfer port
Dave,
I'll stick by my comment –
"For a springer, the gas will actually be heated as it is compressed, then cool as it flows through the transfer port to a region of less pressure." Well actually I added a comma…
Only a springer has a transfer port. Pneumatics and CO2 guns have valves.
There is some point in a transfer port where the port is the least restrictive. At that point (let's call it the "throat") the gas starts to decompress and it cools. At that point the gas is still higher than atmospheric pressure, but it is lower than the pressure in the piston chamber.
Further speculation -> I haven't read Cardew's book, but there are two factors which could cause "visible light" in the transfer port of a springer. The first as you pointed out is the combustion of hydrocarbons. The second is luminescence of nitrogen due to the air being heated. No idea how hot gas in piston chamber gets or how hot nitrogen gas must get to luminescence. (Luminescence is light given off because something is hot. Who lot of reasons some substance might give off light.)
Herb
C Jr/ Chuck,
Hopefully Herb will confirm:
Once you pull up the old post, the comments will be listed directly below it. Leave the little blog window closed; Don’t click on “Comments”.
Go to the browser toolbars at the top of the window and click on “edit”. That will open a window that has “Find.” Click on “find” and type in what you are looking for. That will search through all the comments on that single post.
Lloyd
CJr,
Most browsers will have an option under edit to “find on this page” in which you can enter the text you are looking for. This will work once your in the comments section of the correct post. I know Internet explorer has this option.
John from jersey
Lloyd,
Basically correct, but exactly how it is done and what happens depends on particular browser and version.
FireFox menu item “Edit” the sub-selection “Find” which opens a search field in the window itself.
IE V7 menu item “Edit” sub-item “Find on this page…”. IE 7 then opens a dialog window for the search term.
I have done a lot of software testing… Developers want tester to describe EXACTLY how to recreate problem, not approximately how to do so. 🙂
I also have to test my website with 7 different browsers including two different versions of IE. 🙁 So much for internet “standards.”
Herb
PS – Geeze am I bored today, hence all my posts….
Thanks Lloyd, John and Herb,
I already knew how to do the EDIT/FIND. That is what I explained in my first post about this index thing.
BUT here’s what I didn’t know: I thought it had something to do with the format of the earlier posts but it doesn’t. Instead it depends on how you enter the post. If I come into the post through the Pyramyd site Blog tab or through
/blog//
I cannot search the comments. It’s the same as clicking on “comments” at the bottom of a post and bringing up the comments window. The EDIT option is not available in the comments “window”. See how complicated these things can be?
BTW, B.B. may have already mentioned this, but he did attempt an index in September 2005. Check it out in the archives. He never did it again. Probably still taking Advil because of it. Now with over 1,000 posts it will be enormous.
-Chuck
Herb,
I guess thats a further clarification to the mysteries of springers. Read the book if you can…its absolutely fantasic…and guaranteed to shake up at least one scientific parameter in one way or another.
–Dave
WOW 2.8512 Trillion FPS
Now if they would have stuck an air rifle inside the Helios 2 spaceship back in 1976, then bragging rights would have most likely been endless.
scratch that it’s only 220,00fps.
ajvenom,
Like your basic idea. Eternal bragging rights for velocity will be had by first airgun manufacturer to fire past the Roche Limit into a black hole.
Like Energizer bunny “the velocity is 0.9999c and it keeps on going.”
🙂
Herb
In stores soon the MPE!!!
Magnetic Pellet Accelerator…
with a strong enough magnet, I bet they could throw some lead around.
Perhaps we’ll see a plasma pellet cannon someday or Laser pellets propelled by real lasers.
To the concerned parties:
(Chuck specifically for this one): On the matter of searching for text:
I used to use Firefox, and under the Advanced options menu, there was a tab called General. Under that was a submenu called Accessibility; it had an option called “Search for text when I start typing.” Nowadays I use Safari (I’ve found it to be faster and more stable, at least on my computer); I have an add-on that’s supposed to do the same thing, but it doesn’t work. But that doesn’t matter; I have something called Screen Sieve that allows me to search for text in the frontmost window of any application, including the finder (I’m using Mac OS 10.4.11).
On the matter of an index:
I took the liberty of compiling a rather crude list of keywords for content for the posts in 2005. I only used titles, and even then it took quite some time, and I still need to refine the list considerably and connect the posts to the topics. Based on that experience, I can say that doing the same for the comments will be a somewhat nightmarish task. I’ll give that a stab in my free time today to see whether doing so will be at all practical, or if we should just post an obvious and strong suggestion to use the search function for finding content buried in the comments on the posts.
BTW, I’m a college student, currently jobless, and I go back to school on the 20th. This means I have a considerable amount of spare time right now, and it may just work out that I could do most of the indexing by myself, seeing as I have the time. This also would prevent the need to go through and reconcile any format and/or style differences between the work of different parties.
Watch for my report on the pragmatism and progress of indexing tomorrow..
EJ
BB, approximately what percentage of the power of a strong springer (say in the 15 to 20 ft-lb range) is supposed to be generated by the cumbustion of lubricating oils?
Herb,
I may be wrong in the terminology, but I believe that pneumatic airguns also have a “transfer port.” It is the hole that the air flows through into the breech when the valve opens. If transfer port is the wrong term for this, someone please correct me.
Thanks,
.22 multi-shot
Vince,
I don’t know that a good study has ever been done on that subject. When Cardew removed air from the gun so dieseling was impossible, the velocity dropped about 25 percent, but that was for a gun in the 600+ f.p.s. range. I don’t know if todays magnums would follow suit.
B.B.
To search for certain text on a given page, can’t you just use Ctrl-F?
B.B. or someone else,
RE BB’s comment: “When Cardew removed air from the gun so dieseling was impossible, …”
Was he shooting a springer in less than the standard atmospheric pressure at sea level?
I’m totally confused as to how you would “remove air” otherwise…
Herb
Herb,
Shoot the rifle from a plastic bag. Fill the bag with an inert gas that displaces the oxygen. If the gas used is close to the density of air, like nitrogen, for example, you get a gun that cannot diesel.
B.B.
Herb,
The air wasn’t removed.
What was removed, was de oxigen from the air.
The “air” (gas) used was 100% nitrogen.
The original report from B.B. is here:
/blog/2007/5/what-does-dieseling-mean-part-2/
Regards.
ajvenom,
RE: “with a strong enough magnet, I bet they could throw some lead around…”
Mostly no…
Lead isn’t magnetic but diamagnetic (repels a magnetic field). A super super super duper magnet would be able to repel a lead pellet, but it would be countless magnitudes of energy more efficient to attract a magnetic pellet such as iron. That is the principle behind a rail gun where a magnetic field caused by a strong current propels the projectile down the rail.
A powerful LASER would simply vaporize a pellet not propel it. Basically a LASER would cut a hole through something. A LASER would be slick though. No drop with distance unless shooting near a black hole. (You just have to be careful when shooting squirrels so that you don’t down an airplane after you blow a hole through the squirrel.)
Herb
Well…the action was placed in a plastic bag, and the “air” was sucked out with a vacuum pump, for about a half hour. Then nitrogen was pumped into the plastic bag, the gun fired while still in the bag, and the resulting pellet velocities showed a 45% decrease. He then postulated that the 45% decrease in pellet velocity was due to no combustion, because of the pure nitrogen environment that he created inside of the bag.
It would have been awesome if Cardew would have had his perspex window installed at the time of the nitrogen experiment. Then he could have seen if the white light was still in the transfer port with a nitrogen environment…but I dont remember any reference to that. I still think that the white light is combustion though.
Herb,
The Cardew’s book “The Airgun from Trigger to Target” was written for you.
kevin
Amen
Wow – Since kinetic energy is as velocity squared that means that 3/4 of pellets energy is due to combustion.
White light very well might have been due to combustion. Given the discussion on combustion it does seem very probable. I was just trying to point out that there are other reasons that light might be created. The transitory pressure pulse could cause other weird things to happen. One of my other interest is fluorescent minerals. When it gets really dark your eye can detect a very tiny amount of light.
Herb
I’ve got a UV led flashlight, and love to check out the flourescence of stuff. Its really very fascinating to me. My wife and I put glow-in-the dark plastic stars up on our bedroom ceiling. Lotta fun goin on there…
B.B.
OK, I'll bite. Here are my observations as a trained scientist, (physics and chemistry, and a bit of quantum mechanics).
1. There is no physical sound "barrier". This idea was the prevailing thought right up until Chuck Yeager flew past it, and then proclaimed "no big deal". Now we do it everyday. The SST flew commercial passengers beyond the sound barrier for 20 years.
2. All it takes is enough energy, and we can propel anything past the speed of sound. It makes no matter where the energy comes from, as long as we can focus it as kinetic energy on an object, the object accelerates in proportion to the force delivered.
3. There is no reason a spring piston can't push a pellet supersonic, without detonation. Imagine if you will, a stout automotive coil spring, pushing a piston in a huge cylinder, with a normal air-gun transfer port. A thousand+ foot-pounds of force is going to hit that pellet, and believe me, it is going to move supersonic.
4. I do not agree with the Cardew observations, and I will, at some point, find the flaw in their experiments. I think anyone could get one of these new Gamo rifles, and fire it in a nitrogen atmosphere, and push a light pellet supersonic very easily.
5. Whether the pressure in the chamber increases because of ever-more powerful springs, or the detonation of miniscule trace hydrocarbon, the pellet is still being propelled by high-pressure air exiting the transfer port, and depositing its kinetic energy into the pellet.
The "explosion" does not propel the pellet, any more than the explosion pushes the piston in your car. In both cases, all the explosion does is drastically raise the air pressure in the cylinder, and it is the pressure that exerts the force, and does the work.
5. "Sound" is not air. "Sound" is the vibration of molecules. If you stick a steel rod against your ear drum and tap it, you will hear it. No air involved. Sound passes easily through solid objects.
6. "Sound" in air is vibrating air molecules. In air, the "vibration wave", (where one molecule has to knock the one next to it, and so on), travels very slowly – about 1100FPS. In steel, sound travels much faster.
7. The light that the Cardew thought they saw does not indicate detonation. It indicates light. Many mechanical activities create light. Chew a wintergreen livesaver in the dark, in front of a mirror. Lots of light, your mouth won't explode.
8. Don't get hung up on "diamagnetic". All materials show a diamagnetic response in an applied magnetic field. In fact, diamagnetism is a very general phenomenon. All paired electrons, including the core electrons of an atom, will always make a weak diamagnetic contribution to the material's response. For all practical purposes, lead is non-magnetic. You will not be able to detect any response of lead to a magnetic field, same as aluminum, copper, gold, wood, etc.
9. "Railguns" use a rapidly moving electro-magnetic field to propel "magnetic" projectiles. Again, supersonic is attainable, with enough force. The Disneyland coaster "California Screamer" is a railgun that propels a coaster. (If you watch it on You-tube, you will see them cooling the rail down with water after every "shot". – totally cool)
10. The thought behind "laser propulsion" is to excite molecules at the back of the object being propelled, to the point that they fly off the object. You then have stream of matter leaving the back of the object. For every action, there is an equal and opposite raction, and the object will move forward. (This IS the basic rocket-motor principle).
11. The stability of a pellet in flight is disturbed when the vibrations of the sound produced, catch up to the pellet. This should not be considered strange. Vibrations will destabilize anything, because vibrations are nothing more than molecules whacking into things. Consider if you were standing quietly, and got hit by a thousand golf-balls. Destabilizing, yes or no?!?
12. HOWEVER, if you can propell the pellet fast enough, so that the vibrations can't catch it, then problem solved. If you can launch a pellet at 1300FPS or so, and hit the target above 1100FPS, you have a great thing. There are plenty of rimfire cartridges, (those neet .177s) that fly at 2000FPS. It's a great thing for lousy hunters like me – nice flat trajectory way out.
I have a chronograph, and here are some things I've measured. My normally 950+- Gamo CFX readily goes into 1200FPS with too much oil in the chamber – detonations for sure.
My Infinity, (with neighbor Dan pumping to 3300PSI), easily blows 13-grain H&N match pellets at 1250FPS. I have discovered, however, that I can hit nothing at 35 yards. (Waiting for Eunjins – but also Crosman Premiers).
Very interesting topic. For me, the lousy hunter, if you can sell me a 1500FPS rifle, so I can shoot supersonic out long, I'm buying…
Best regards,
Jane Hansen
And…there was silence on the blog as everyone pondered what fantastic things Jane just said.
WOW. Jane…I’ll buy that rifle too!!!
Jane! I’m glad you chimed in. I’ve also wondered about the Cardew conclusions, and today I ran some numbers, all approximate but certainly (I believe) in the ballpark…
If a gallon of oil has about 100,000,000 ft-lbs of energy per gallon, I believe that comes out to about 1700 ft-lbs per drop of oil. If three drops of oil are added to a spring-air gun every 5000 shots (which I believe is a fairly liberal lubing), that works out to a maximum of about 1 ft-lb of energy added from fuel burning per shot.
And that’s IF the oil is combusted completely, and no unburned oil is expelled either through the cocking slot or the barrel. And that’s also assuming that 100% of the energy from combusting the oil is transferred to the pellet. Of course, this also assumes that no lube is left in the gun at all after those 5000 shots.
Neither of those assumptions will turn out to be true, of course… so the average energy transferred to the pellet would be considerably less. I’ve also wondered about oil burning because of the lubricant’s tendency to stick to the cylinder walls – and how that can even prevent gasoline from completely combusting in an IC engine.
Does these conclusions seem valid to you?
Hmmm… to all, please forgive the grammatical errors in my previous post. I promise to do better next time. I really does!
WOW! The information and intelligence on this blog never ceases to amaze me. Thanks Jane and everyone else.
Jane,
We’re in violent agreement….
I’d quibble about not getting hung up on diamagnetic. Either a substance is magnetic or not. Magnetic substances concentrate the lines of force in a magnetic field. Non-magnetic (two dollar word is diamagnetic) substances decrease lines of force. Thus a lead ball would be “repelled” by a magnetic field. Experimentally the effect is so small that it would virtually impossible to measure.
I agree about your remarks on sound barrier in general. “Speed of sound” would be a better expression than “sound barrier.” The two terms are used interchangeably which is really improper.
I agree that you can get a pellet to go supersonic, but you couldn’t get to any infinite velocity with a spring piston gun shot in air. I’d be curious what the upper limit would be. Since the gas molecules have to be pushing on the pellet to accelerate it, there has to be some relationship between the velocity of the molecules in gas and the ultimate velocity of the pellet. Since there are three degrees of freedom of motion, I just guessed that if all the kinetic energy of the gas molecules was going down the barrel that three times the speed of sound would be the ultimate limit for a springer.
I also would quibble about Cardew’s observations without actually having read his book. I can absolutely believe that a significant amount of energy in a springer comes from detonation. I don’t know exactly what he said was possible in a nitrogen atnmosphere. I totally agree with you that going faster than the speed of sound (as measured in pure nitrogen) should be possible in nitrogen.
Your reference to the wintergreen livesaver was interesting. It is due to triboluminescence. Basically the flakes that break off end up with a static electric charge. The discharge across the “gap” between the charges causes a “spark,” and that causes nitrogen molecules in air to fluoresce. Did this with my daughter for girl scouts.
Your point about stability of a pellet above the speed of sound is a point that BB has also made many times. I believe you both. Somehow though you’d have to be able to increase the spin rate of the pellet to turn it into more like a bullet than a pellet at supersonic speeds. If you did that the flight of pellet would be stable until the velocity started dropping down at which some point the flight would be unstable again. If the pellet had a diablo shape, when the pellet gets below the speed of sound it would stabilize again.
Herb
Vince,
RE: Energy in oil due to combustion
Not sure about 100,000,000 ft-lbs of energy per gallon, but the rest of the calculation looks good.
a gallon is about 4 liters, 1000 milliliters to a liter, 20 drops to a milliliter.
Herb
wow,if you combine LOYD’s chrony results that show the RAPID loss of fps at very short range,with Jayne’s description of destabiling air molecules at the speed of sound…now I totally get “IT”.first the pellet makes a mess of the air molecules,then slows enough to be destabilized by it’s own mess.Karma and the flight of diablo…has a nice ring to it.FrankB
Actually, since kinetic energy (KE) depends on velocity squared, if all the kinetic energy were going down barrel , then ultimate velocity would seem to be about square root(3) times speed of sound or about 1.7 * speed of sound.
Herb
Herb, I found a conversion that worked out to about 56,800 drops per gallon, your numbers come out about 40% higher. If I used your figures, there’s even less energy in the oil. The energy/gal figure is for fuel oil/kerosene/diesel fuel, which is between gasoline and crude (which themselves only differ about 20%). Again these figures are gonna be ballpark.
Using my numbers, even if half the energy in the oil gets to a pellet, say 1/2 ft-lb, on a Gamo Shadow shooting a 7.9gr Premier, I’m calculating that out to a difference of about 16fps.
I sure wish I had a complete description of that Cardew experiment – along with the specs of the rifle they tested (spring specs, preload, piston stroke).
Herb:
Strictly speaking, diamagnetic is not the same as nonmagnetic. “Lines of force” is a purely human visual representation of a magnetic field. “Lines of force” do not exist. Diamagnetism simply means that most substances, (because they contain base electron pairs), will set up a slightly opposing field, when placed in a magnetic field. Even magnetic metals exhibit diamagnetic behavior. You are correct in that it is virtually unmeasurable.
There is no logic to your “three degrees of motion” and “three times the speed of sound”. Think of air molecules as tiny BBs. They can go as fast as something can push them – far faster than three times the speed of sound, and thus can propel a pellet that fast as well.
The speed of sound in Nitrogen is about the same as the speed of sound in air. My point here is that the dynamics of a spring piston gun, (assuming we can eliminate detonation), are not limited by the speed of sound, or the need for detonation.
Theoretically, the “ultimate velocity” has to do with “universal speed limits” and relativistic motion. These concepts transend Newtonian physics. We do not need to worry about them. There are projectiles shot at 3000 – 4000FPS routinely. We could, if we put our minds to it, make a spring-piston gun that could shoot as fast. (It’d be mighty hard to cock). The point is, there are no laws of physics that tell us we can’t.
The shape of the pellet won’t help us as it crosses the “sound barrier”. It gets knocked off course. We can’t get it back “on-target” whether it stabilize or not. I believe that the diabolo shape is stable at any speed – it just can’t deal with that moment of flight where it gets battered by the sound waves. A normal bullet doesn’t handle it well either.
Comments on oil and combustion. First, for such calculations, we convert oil to energy content, not force. (Footpounds are force units, we need to work in joules, BTU, therms, etc). This would tell us what the energy “available” might be, but without some very sophisticated experiments, we don’t have a clue how much of that energy goes into increasing the chamber pressure.
An internal combustion engine is only about 15% efficient – most of that “theoretical energy” gets lost as heat, sound, incomplete combustion, etc. We have no way of knowing what the efficiency might be in a springer chamber. Detonation is a highly random thing. I personally believe the effect is of no commercial concern. Most of us can tell when we have a detonation – that particular shot sounds different, smells different, and flys different.
Good catch on the triboluminesence. There is also thermoluminescence, photoluminesence, phosphoresence, etc., etc. Just because we see light, we should not assume combustion.
Now, just a thought on the commercial limitations of all this.
For current state-of-the-art, an average size rifle seems to need about 35lbs of cocking effort to get that first 1000FPS. Yes, we can jigger with the length of the levers and barrels, and get some slick linkages, but we don’t really change too much. Sooo – for practical limitations, (considering conservation of energy and all those other laws we can’t break), to get to 1500FPS, (with normal lead pellets), we’re going to need some 45-50lbs of cocking effort. Guess what – that probably puts a lot of people out of the game.
My guess is the Gamo engineers have all sorts of springs in their parts bins, and have flown some pretty fast pellets. I also suspect, however, that the marketing department is keenly aware that we are not all gorillas, and the current velocity of springers is commercially limited to things that are practical to build, (ie-small, light, and inexpensive), and easy to use.
Best regards,
Jane Hansen
Jane,
Thanks for your response. Great fun for me….
You’re right, I was using non-magnetic and diamagnetic as though there were interchangeable which is wrong.
I know that “lines of force” is a model but so is all of science! The model just gets more and more sophisticated. Hard to explain notion so that most can follow and not trip myself up. (ie, now I’m quibbling that you’re quibbling about my quibbling!)
As fast as “ultimate velocity,” I’m not considering something even close to a relativistic discussion about breaking the speed of light.
I agree that I’m struggling to express the notion correctly and adequately, but I just don’t believe that a gas can be pushed as fast as one desires.
Consider a cylinder with two frictionless and massless pistons 10 cm apart. You move the one on the left 1 cm at 10 times the speed of sound in a square wave velocity curve. That will create a pressure wave pulse in the gas which moves through the cylinder towards the other piston. The pulse can’t move faster than the speed of sound since the gas is compressible. Also as the pulse moves it will spreed out. So:
(1) The left piston will be stopped before the right piston moves.
(2) The second piston will never move as fast as the first piston.
Herb
Jane,
To beat this to death, it goes back to the point that you made long ago. “Has a rocket scientist had any input into the design of the transfer port?”
Imagine that the springer compresses the gas in the piston chamber, the piston stops dead at the end of its forward motion, and a StarTrek force field blocks the transfer port. So the gas is compressed and is at equilibrium. (Molecules traveling in all three directions with equal distribution velocities.) Now we release our StarTrek force field blocking the transfer port. Because the pellet is accelerating down the barrel the gas molecules are not at equilibrium. There is a preferred motion down the barrel. A well designed transfer port would convert the maximum amount of kinetic energy of the compressed gas into gas molecules traveling down the barrel.
But ultimately there isn’t more kinetic energy than is in the gas originally.
Right?
Herb
How fast can an airgun shoot –
First, I have to admit I thought this blog was going to be about rounds per minute, which I felt was an odd topic.
After a quick scan, I realized we were back to our old friend velocity.
Wayne, my buddy – in this case I could not agree with you more that velocity takes a back seat to accuracy in pellet rifles.
My mind still has the imprint of the photos from the 1970’s era ARH catalog. Fox, raccoon and more all taken with rifles that would be considered anemic by today’s speed freaks.
Obviously, paper doesn’t take much kill’in. Field target folks prefer less than 20 ft lbs as to not destroy the targets.
So I’ll assume that the need for speed is to send critters to the promised land. The only issue is that any pellet rifle and shooter need to deliver the payload with precision to be effective and humane.
A pellet travelling at 1500 ft per second is still not going to make up for a lack of marksmanship like a centerfire rifle will. Sure, a 22-250 to the mid point of a groundhog will make quite the impression. One such unfortunate recipient at close rage required that I get the hose out to spay down the tomato plants. You simply will not get that “benefit” from a pellet rifle.
I will agree wholeheartedly with the flatter trajectory benefit, but only with a standard weight pellet. The light stuff is like the cork out of a champagne bottle, quick to start, but peters out fast.
In .177 my preferred range for hunting with normal to heavy pellets is 925-985 fps. In .22 caliber I’ll settle for 100 fps less with no problem. My bottom limit in any caliber for pests is 600 + fps. I know some guys with the 10 meter guns or an R-7 are happy with less, but just my opinion. In .25 cal a 600+ fps rifle will actual give a respectable 16 ft lbs or so, just don’t stand too far away.
Volvo
Jane,
Great to hear from you. It warms the cockles of my heart to know that you have animal instincts. You took B.B.'s bait.
Fascinating discussion/theory.
Now that you have a chrony and a pcp (Career Infinity direct from Japan. Great story!) I have a question. Have you identified a "broad flat spot on the power curve" where you have a narrow spread of FPS or is it a straight drop down in velocity? Although you've tried the H & N's 13 gr. and are awaiting the CP's at 14.3 gr. and heavy eun jins at either 28.4 gr. or 32 gr. have you considered the "medium weight" pellet that everyone is raving about for the career infinity…the new jsb 18 gr.? Just a thought for you.
I have one last question. Forgive me. I struggled to advance past 6th grade. They didn't want me I wasn't interested in them…long story. Another time.
You said, If you can propell a pellet fast enough so vibrations can't catch it then problem solved (improved accuracy). If you can launch a pellet at 1300 fps, or so, you have a great thing. But, your 13 gr. H & N's are doing 1250 fps and "you can't hit nothing at 35 yards". Do you think another 50 fps will give you the accuracy you're looking for?
I'm interested in accuracy and want to understand every way available to achieve it but this runs contrary to all I've experienced and read about considering the pellet weights we're discussing at the assumed fps's you're hoping for/would buy at (If you can sell me a 1500 fps rifle, so I can shoot supersonic out long I'm buying). I understand the theory but you've shortcircuited my experience. Help me if you can.
kevin
ps-If you didn't already know, this is "Help a Redneck Week". Please do what you can.
kevin
Gentlemen,
Having read Cardew’s (and Mann’s) books, I can tell you that you are missing about 15 minutes of interesting reading in books that require over an hour each to read.
I wish one of these characters had used a good editor….but then these would have become good magazine articles instead of dry, dusty, obscure and impractical tomes. Mann’s book is particularly esoteric…unless you are getting ready to lob some aritillery shells.
In no way are these books worth the $55+ for each via several used booksellers. I would say, rather, that they supply about $6 worth of information.
I do own and enjoy re-reading several other airgun books from time to time, including using for reference…but not these!
Don’t be tricked by a friendly book review! I am telling it to you straight. I know what airgunners like, and it’s not these books.
– Dr. G.
Re: Chaos due to motion faster than the speed of sound
Just because a projectile moves faster than the speed of sound doesn’t mean that it will be stable. It has to spin too. It is the spin that “averages out” the “vibrations.” If it isn’t spinning the “vibrations” will certainly “catch up” with the pellet.
How fast a diablo pellet and a bullet have to spin is different.
Herb
Dr. G.,
Had no intention of “Tricking” anyone with my “friendly book review”.
I’m an airgunner and I liked the books.
Wow. Talk about lobbing “some artillery shells”.
I respect your experience and advice. What airgun books do you “enjoy re-reading”?
kevin
Kevin –
Hope you don’t mind if I jump in, but don’t feel overly obligated to achieve a perfect fill every time when your mystery PCP arrives. Last night I wanted a little more time with the FX Whisper but did not feel like putting a full tank in it. Anyway, I gave up pumping at about 160 bar. Curious as to the result of this I broke out the Chrony, the first shot with Beeman FTS was at 974 fps and after that they stayed within 2-3 fps for the whole magazine. The last shot out of the second magazine, #32 was at 966 fps. No, 160 bar is not the ideal fill but no one is handing out gold stars. Sometimes we make things more complicated then they need to be.
Wayne,
The FX Wisper is also available with a walnut stock, but I think now you should go for a Moonsoon. A semi-auto is not an option for me with a hand pump, but that would be something very different for you. Or maybe get the Air Arms semi-auto.
Volvo
ZeChico,
thanks for the link back to BB’s old blog. I was so busy talking I forgot to listen.
In the part “Is fuel even necessary?” – I guess the Cardews didn’t realize that graphite burns too! BB didn’t mention velocity they got with graphite lube.
Herb
Volvo,
Thanks. I have a bad habit of overthinking things. Even those that don’t matter much.
Again, thanks for the link to the yellow regarding ongoing healthy discussions about the FX whisper vs. the AA S410.
kevin
Kevin,
“Total Airguns” by Wadeson and “Airgun Odyssey” by Hanson, and of course the Blue Book are my three favorites.
BBs blog and posts, if put together, are the equal of any of the above books in terms of theory and practice.
As for “tricking,” I suspect that Cardew’s nephew must have gotten to you, just as we all know that The Men at Air Arms have obviously gotten to Wayne.
– Dr. G.
Kevin,
Sorry if my suggestion came across as a criticism, it was not meant to be in the least.
Just wanted to share what little I have learned about PCP’s so far. One of the reasons I think I held off for so long was all the complex analysis that gets tossed about.
Nothing wrong with that sort of thing if it’s your cup of tea, but it is not crucial.
Just ad pellets and air as needed, then pull the trigger.
Volvo
Dr. G.,
Thanks.
Not related to cardew. No limey blood here.
As stated, cardew appeals to the scientist in a few people (Jane & Herb?). I think it's an interesting read, not a fun read. "Muddle through" as I said in my juvenile book report. Verified hypotheses.
Airgun Odyssey seemed self serving. Nothing but higher end guns reviewed. His chest beating about long range hunting with an air gun and my perceived arrogance about his view of FT was a turn off for me. Just my opinion.
Never read Total Airguns. With your recommendation now I will. Thanks.
Blue book is my second bible.
Couldn't agree with you more that if B.B.'s blogs and posts were bound that they would be equal or greater than any of the books I've read in terms of theory and practice. Is there an idea we should act upon here?
kevin
I did a quick run of numbers to find how much energy oil could give to a pellet for 100% burning and 100% efficiency (both of those assumptions being complete and utter BS of course), and my numbers came out just a tad over over Herb’s.
Jane,
the foot-pound is a unit of energy. If you may recall, energy is in the same units as the work done by a force across a distance. The pound is the force in question, and the foot the distance. For reference, the foot-pound is defined as being exactly 1.3558179483314004 Joules. One might also come across the foot-pound in the context of torque also; I have sometimes also heard it (the unit of torque) called the pound-foot in that context to avoid misunderstandings.
How much energy goes into compressing the air in the chamber? Well, what is the state of the air prior to compression (volume, temperature, pressure etc.), and while it is most compressed? In fact all we need to find the energy of compression is the change in volume’d1 the changes in pressure and temperature can be calculated using the appropriate variations of the ideal gas law as pertaining to an isentropic process. Incidentally, if one were to pull the spring out of an airgun of known change in volume (and therefore energy required to compress the air within), one could then empirically determine its spring constant using Hooke’s Law. Using that data, the compression data, and Hooke’s Law again, and taking into account any prestressing, one could also find the potential energy stored in the spring when the gun is cocked, and therefore find out how efficient the spring is at compressing the air, or propelling the pellet (in terms of its kinetic energy), or both I guess. One might also approach the problem in terms of Gibbs free energy of the various states of the air (initial, compressed, etc), but that, frankly, would be an absolute pain in the rear end.
Obviously the above approach assumes an ideal gas (which air is not); there are various losses due to friction, sound, internal losses in the spring, compression of the actual gun components, etc. However, I very much doubt that these would be very significant aside from the inaccuracy due to air being a non-ideal gas. In fact, should the gun get any significant amount of energy due to combustion that gain may well outweigh losses to friction, sound etc.
Incidentally, I did a quick-and-dirty use of the ideal gas law approach to determine a (very) rough determination of temperature in a medium-high powered springer some time ago; I do not remember the number I got, but I do remember that it was the exact same as the lowest autoignition temperature I could find listed for silicone oils. As rough as my calculations were, I doubt that I stumbled upon something that was in the realm of pure coincidence.
That brings me to another quick thought— flash points don’t really matter when considering oils. The flash point of a substance is the minimum temperature at which its vapors will ignite in the presence of a much hotter external ignition source. Assuming a vapor sample doesn’t gain much energy from an ignition source beyond that needed to ignite it (i.e. the vapor doesn’t warm significantly), the vapor will stop burning once that ignition source is removed. So unless there’s a spark plug in your air rifle, then flash points are also moot points. There’s also a temperature just a bit higher than the flash point called the fire point; this is the temperature at which the vapor will continue to burn after the source of ignition is removed. By contrast, the autoignition point is the point at which the vapor will spontaneously combust without need for an external ignition source. Autoignition points are typically much higher than flash and fire points.
Wow, this ‘comment’ is getting quite long, and it’s getting quite late.. There’s more I want to talk about (in terms of physics), but I think I’m just going to post this thing then go to bed. If I’m lucky someone might even see it too ;[
Volvo,
What you shared was not taken as criticism. I’ve always felt like I’m walking in your shoes but at least a mile behind you in the airgun world.
Your entrance into pcp’s after a lengthy dedication to springers contributed greatly to my willingness to experiment. I appreciate it my friend. Something new. Exciting!
Although your experience wasn’t intentionally directed at me it had a profound impact. Please keep those comments and advice comin! I have $43.00 left in the bank and have no idea what to do with it. Suggestions?
kevin
Wow! Quite a discussion.
There are a couple things I am questioning.
First, a diabolo shaped pellet, from what I’ve read, seems to slow down faster than a bullet shaped projectile. Even if you get the diabolo pellet going faster than the speed of sound, it would then slow to under the speed of sound quicker. That will limit its range.
Second, it seems like you lose part of the advantages of airguns if you break the “sound barrier” or go to bullet shaped projectiles. Breaking the sound barrier makes the gun louder and using bullets makes them travel further (reduces safety).
Is this correct?
So, you could probably take a high power Quackenbush or Dragonslayer rifle, put a small caliber barrel on it, use a bullet shaped projectile and get a gun that shoots supersonic, has a pretty flat trajectory and long range. The question is, isn’t this basically a .22LR and would there be a market for it in an airgun?
.22 multi-shot
Kevin,
Just be careful were you walk. I tend to step in a good amount of cow patties. Just finished shooting the Raider for the night. Just like in “real guns” a single shot bolt is nice in that it will eat anything. It is a little weak for the .22 cal Kodiaks but they are dead accurate. They have such a well-made feel. On the other hand, I think the EunJins look like maybe they were whittled with a penknife.
I’m calling it night. Volvo.
Jane,
I would start with the 21gr kodiak, and try the new 18gr JSB, I haven’t yet… The Eunjins will be great for foot lbs. and pretty accurate out to 40 yards probably 3″ 5-shot.. The 21gr kodiak should give you a 2″-5 shot group at 50 yards.
Again, if I were trying to keep tight groups or hit a small kill zone.. I would keep that 21gr kodiak at 900fps or less, even if you have to “loft” it..
In a rest, with the AAs410, I can loft a 5″- 10 shot group of 10.6 kodiak at 75 yards pretty consistently, and have had some 2″… The 16gr. Eunjins, on the other hand are side ways and a 10″ or larger group… so it just depends on your kill zone I guess..
Volvo,
I just saw the walnut stock Whisper today on a site.. very, very nice.. I’m sold except for no power adjuster.. I noticed today that the standard stock, used one is still on the yellow for $750.. three days now.. you got yours for $650? that was a great deal.. let me know when you move up again..
Randy and I were just talking about the news that we really can’t shoot a multi-shot in a serious FT contest.. can’t as in, not allowed.. not as, you might dry fire..
So, we decided to set up some moving targets for the Air Arms S410 side lever.. and others like that.. so I will be adding fun multi-shots this early spring as the raised beds provide:):)
Hey guys, this sport is about SHOOTING!! test enough to find your sweet spots, know your gun.. and..
Watch less TV, read less, write less, blog less, and SHOOT MORE!! Except for you Vince, you keep fixings and making that special red ryder.. the air gun world depends on that 4,990 feet per second entry level kid gun..
besides I’ve already printed the catalogs.. I hope what you come up with matches our photos..
Wayne,
Ashland Air Rifle Range
We already have the technology to go much faster. Check out this link from wikipedia https://en.wikipedia.org/wiki/Light_gas_gun
I would think that you could substitute a spring for compression instead of powder, you may not get quite the same velocity but 6 kilometers per second might have a bit to much kick to it.
Jim L.
Question: if we would make a smaller diameter pellet, eg 2mm instead of 4,5mm(.177), then the pellet would have about the same energy delivered to it as a .177 (less actually, but close to), and would subsequently fly faster. So, if it is flat trajectory we want (for Field Target or HFT), why don’t we make a smaller caliber pellet? Surely it could could stay hypersonic to 50 yards.
It would also be a good way to study airrifles dynamics.
Hey EJ-
Your approach on an index sounds like it is light years ahead of mine. I was thinking of taking the "subjects" approach but what you are talking about would be a true index. If you can pull it off I would take my hat off to you (I'll do it anyway for making the attempt).
To all those index naysayers- Searches are great when you know the right keyword to use. When you are a newbie the keyword thing can be a big hurdle. I say an index is just another tool in the toolbox. If somebody else is willing to do the heavy lifting where is the harm? End of rant;->!
Go EJ!
Gavin
RE: At January 09, 2009 12:27 AM, .22 multi-shot
I think all of your points are on point.
No “shroud” is going to quiet a supersonic gun. The projectile (bullet or pellet) will make a heck of a noise by itself.
The “reason” for a 0.22 pellet gun to me are exactly the points that you raise. It is safer since the pellet won’t go a mile. It is quieter so that it doesn’t attract attention.
Herb
RE: Kenitic theory of gases, springer, and max speed of pellet
Dah….
Finally dawned on me. When I calculated roughly 1.7*speed of sound as max, I was calculating based on a pneumatic, not a springer. For a pneumatic the temperature actually drops a bit. The transfer port acts as a nozzle to direct the gas molecules down the barrel. That’s where the three degrees of freedom comes into the mix.
Jane is right in her point:
“3. There is no reason a spring piston can’t push a pellet supersonic, without detonation. Imagine if you will, a stout automotive coil spring, pushing a piston in a huge cylinder, with a normal air-gun transfer port. A thousand+ foot-pounds of force is going to hit that pellet, and believe me, it is going to move supersonic.”
What happens in a springer is that not only the pressure of the gas goes up, its temperature does too. The increase in temperature gives the gas molecules more velocity. So the pellet will zip out of the barrel at supersonic speed. The gas heats so quickly that the heated gas doesn’t have time to cool down to ambient temperature. You can effectively get the gas as hot as you want by using a bigger spring. Thus a bigger spring yields more velocity. Well at least until things start to melt…
Herb
“The gas heats so quickly that the heated gas doesn’t have time to cool down to ambient temperature.”
The gas heats up when it is compressed. The compressed gas flows so quickly through the transfer port and down the barrel to accelerate the pellet that it doesn’t reach ambient temperature.
The other thing here is that for a springer the piston does recoil. The recoil starts before the pellet leaves the barrel. Think the pellet reaches max velocity in something like 6-8 inches if I remember BB’s past comment correctly. So a short barrel and a long “shroud” to act as a level would max performance.
Herb
Wow:
Lots of good science is evident in this crowd. First, let me make a distinction. A "foot-pound force" IS a unit of energy, and "foot-pound" is not. One foot-pound force is the amount of energy expended when a force of one pound acts through a distance of one foot along the direction of the force.
We keep this (pointless) distinction in our minds, because – think this one…we can exert a force on things (a very large force, for a very long period of time) yet expend NO energy. Anyway, it is a problem I have of just being too precise. For our discussions, I need to let go.
Some final comments on the science.
1. The 2-piston experiment in the cylinder is a great process, but doesn't prove our point. Let the first piston go farther, faster – what happens, the density of the air increases, the speed of sound in the cylinder actually increases, and the pulse can move relativistically supersonic, (ie >1100FPS) with no problem at all.
2. We simply need to forget about the speed of sound as some sort of magic number – it isn't. Air molecules travel supersonic speeds all the time. The exhaust of a fighter jet is loaded with particles, (air molecules), that are moving at supersonic speeds.
3. The "force-field" transfer port is a great thought experiment – It gives us time to think of what can happen in the chamber – the air compresses, temperature rises in response to spring-pressure, pressure rises in response to temperature…a very convenient way to convert the energy stored in the spring into energy stored in compressed air. We can take the thought further – we can burn some hydrocarbons in the chamber and get even more pressure.
We release the force-field, the molecules exit the port and start pressurizing the space behind the pellet, (exterting a force). The speed, (acceleration) of the pellet is determined by how much force is applied, and how much time we apply the force. The speed of sound, (for lots of reasons), does not need to be considered. We know springers send pellets supersonic.
4. Let's switch to something more practical. My ultimate desire is to have a muzzle velocity as high as possible. Why, bacause the higher the speed, the flatter the trajectory, and the greater the "depth of field" I can hunt in, without having to adjust for elevation – remember, I am a lousy hunter.
5. Accuracy is hindered any time we cross the "sound barrier".
6. I have 2 options. Get as close as I can, and stay below, (hoping this would be about 1000FPS), or get above, and stay above.
7. Problem as I see it – pellet/barrel design. These are almost all "subsonic" design combinations. The optimum spin of the pellet changes with velocity, but not at the rate that is in proportion to the barrel twist. (at 1300FPS, we're spinning them all too fast)
Thus, each barrel-pellet combination will have an optimum velocity. Since we don't change our barrels, each rifle will have an optimum pellet – (for more reasons than just this).
So, I'm trying to find that optimum pellet that will get me as much accuracy and velocity as possible in my Infinity.
So far, I have experimented with just one pellet. (more on order). So far, the Infinity will give about 36 good shots before it drops off to <900FPS, (set on low power) Below that, I am not interested. The velocity falls off rapidly at first, (1100 down to 1000 in 6 shots), and then falls steadily and slowly for the next 30 shots. No valve lock – but little self-regulating of the valve. Makes me wonder if I should lighten the hammer-spring.
Any suggestions would be greatly appreciatated.
Jane,
RE: “Makes me wonder if I should lighten the hammer-spring.”
I’d resist the temptation to modify gun until you get more familiar with it.
—-
RE: Number of shots
I doubt that you’ll get more than one shot at the varmints before the rest run for cover. My experience with squirrels is that get skittish quickly. So I have to position myself like a sniper to even get a shot. One is all I get at a particular time.
I doubt that being able to shoot a string to 20 shots will be advantageous in whacking varmints. Practice yes.
—
Re: Type of pellet
I’ve played around with a couple of multi-pumps and a wide variety of pellets. Besides precision, I’ve been amazed how much the POI moves around with different pellets.
The combination of gun and pellet seems to be a mysterious match. Of course pellets that others have found to work with Infinity would be a good bet.
Although the various hollow points would expand with the Infinity, I doubt they will be as accurate a good domed pellet. But first you have to hit the varmint in a vital spot to kill it. I kept thinking I’d be able to find a pellet that would blow a squirrel apart, but none of the multi-pumps has anything like that power.
BB indicated to me that I should think like a buffalo hunter where shot placement was key. That was really kind of novel to me since I hunted birds with shotguns. If you hit the bird you’d generally put 2 or 3 pieces of shot into one, and one of those would be fatal. So I was just trying to hit the bird, not pick a spot on it to hit.
——
RE: Velocity wanted
I keep thinking about a PCP. I can’t have a lot of noise in a city yard though. Anyway It seems from comments that many have made that 900-1000 fps is a “good” velocity zone. Faster and you get near speed of sound which causes flight instabilities because the pellet isn’t spinning fast enough. So I think you’d need a domed pellet that would be heavy enough to keep you in this sweet spot.
—-
Re: spinning
Seems like pellet rifle barrels were made with machines used to make firearm barrels. It worked good enough so none of the manufacturers seems to have extensively studied spin problems.
To spin pellet faster it seems that you’d need a variable twist rate. A pellet doesn’t have as much contact as a bullet with the barrel rifling. So I think that it is easier to “strip” the contact surface of the pellet off.
Herb
Could anyone comment on the idea of above poster about making a smaller caliber pellet? It would go faster wouldn’t it?
From what I see, It will go faster.
But will have much less energy, because its harder to transfer energy to a smaller caliber.
A smaller caliber will also be less deadly.
Andrew,
A .14 caliber pellet has been tried. It went about as fast as a medium-speed .177, but presented loading problems, barrel-making problems and was generally not worth the effort. This was just an experiment, so perhaps with more work the idea could be refined.
B.B.
RE: Smaller caliber pellet.
This all gets tied up in discussion about how fast you can push a pellet with compressed gas. I figured out my mistake, and there isn’t a limit. I’ll post to BB’s next discussion on “how fast…”
The kinetic energy (knock down power)is given by:
K.E. = 1/2 * m * v^2
where m is mass of pellet and v is velocity.
If you look at various rifles that are offered in 0.177 and 0.22 (using the exact same power plant, just different barrels) the 0.177 has a higher initial muzzle velocity. But the 0.22 version will have more K.E.
As the 0.22 pellet goes downrange, it will retain more of its K.E.
Since getting near the speed of sound fouls up the flight characteristics of a pellet, and since it is already possible to get a springer to shoot a 0.177 and a 0.22 near the speed of sound, the underlying question here is why would you want an even faster PELLET?
By PELLET, I think the diablo shape is implied. If you want to use a bullet, then you could probably get the projectile going fast enough with current powerplants to greatly exceed the sound barrier and be shooting an air rifle at 0.22 LR (firearm) velocities and using a bullet.
The whole bullets vs pellets thing is a very fundamental and profound setup difference.
I’m shooting in a city and I wouldn’t dare send bullets after squirrels. A 0.22 LR from a firearm could easily hit someone or something at great distance and cause harm. Frankly I’d feel safe shooting my 12 gauge shotgun UP into a tree, but the police would be attracted to the noise like flies to honey. The shot falling to the ground would cause great consternation even though the danger would be low.
There are gentlemen now shooting air guns to hunt big game. They use bullets not pellets. It isn’t an cost efficient way to hunt. A firearm could be purchased for a lot less with a higher velocity. It is however more like bow and arrow hunting. You have to stalk the game and get closer. I was enthralled with BB’s description of the stalking in a big bore hunt. Climbing into a fire watchers tower as a “stand” and shooting a 50 caliper rifle 4 miles on a private preserve isn’t much of a “hunt,” it is target shooting.
So I’d think that an air gun of 0.177 caliper or so shooting a bullet at 0.22 firearm velocities would be possible. But frankly making such a mass produced commercial weapon would hasten stiffer regulations on air guns. With the push for big bore hunting, I think that day is coming. Other countries have much more restrictive regulations on air guns than the USA.
There are some practical limits on how small you can make a pellet. You can’t just scale it down. The walls of the skirt have to be thick enough to be handled without deforming. I ordered some Mendoza hollow point pellets to try them and they were awful. the head was hollow, but the “skirt” was completely filled with lead. That made the pellet “tail” heavy and the flight characteristics were just plain bad.
The above is the “Dad” answer. The “Mom” answer is “Yes, it would go faster.”
Herb
Re my comment – I figured out my mistake, and there isn’t a limit. I’ll post to BB’s next discussion on “how fast…”
Maybe yes, maybe no 🙁
Crudely what happens is that you convert the potential energy of the compressed gas into kinetic energy of gas molecules. The out flowing gas then transfers energy to the pellet accelerating it out the barrel.
It is now clear to me that the type of powerplant of the air rifle makes a difference.
A springer heats the gas as it compresses it. So a springer increases both pressure and temperature of the gas above ambient.
For a pneumatic the work is the volume, V, of the pressure chamber times the change in pressure before and after firing. A pneumatic has to have something in between adiabatic and isothermal expansion. Due to the speed of the firing cycle adiabatic expansion is probably closer.
A CO2 is a special case of a pneumatic. There is an upper pressure limit where CO2 gas becomes CO2 liquid. There would also be two different limits for a pneumatic. First if gas is injected into the barrel, and second if liquid CO2 is injected into the barrel.
The point I’m struggling with is the kinetics. For a pneumatic obviously there is no limit has to how much work can be done by dumping the whole pressure charge. But obviously if a Talon SS dumped its whole fill on each shot all of the energy doesn’t get transferred to the pellet.
On the surface it seems to be a simple question. But the mathematical analysis isn’t trivial.
Herb
Two rather interesting articles on nozzles and gas flow.
figure 2 in this article shows two nozzle designs with much difference in their performance. Goes directly to Jane’s earlier question – Has rocket scientist been involved in transfer port design?
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080008561_2008007439.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060004779_2006004484.pdf
Wonder if we could get these guys to design air gun transfer ports? 😉
Herb
hi bb,
i recently bought a rws 850 airmagnum in 22 cal, and i have a few questions. I put this up on the old blog, but in a nother message it said to go to this instead because its more recent. Can i shoot the gamo raptor pellets out of this gun?? are they accurate?? and also where i live in the winters it gets between negative twenty eight to 37 degrees fahrenhiet will this gun be able to shoot well when its about 30 degrees?? and in the summer its good temperature for this, but it is about 70 to 90% humidity? will that cause rusting??
thanx,
Myles
Myles,
Here's the answer I left where you originally posted your question. kevin
At January 18, 2009 9:33 AM, kevin said…
Myles,
Let me start by saying I've never owned an RWS 850 Magnum but I want to try and help you.
First about gamo raptors. I've never shot a gun that grouped these pellets very well in either .177 or .22. There are a lot of good reviews on the Pyramyd AIR site about pellets that work best in this gun. Go the the top of this article where B.B.'s review begins and in the first sentence and click on the underscored words "850 AirMagnum". This will take you directly to this gun on the PA site. Scroll down to the bottom and read the REVIEWS on this gun. What I read in the reviews of this gun by others is reflective of what B.B. said in this article, "850 likes mid weight pellets. JSB's were most accurate". Don't let these reviews or even B.B.'s experience with one gun sway you from trying any pellet. Your gun may group pellets best with a different pellet.
Low (cold) temperatures can affect CO2 performance. If it's cold try warming your CO2 cylinders before going out to shoot. Cold and humidity won't hurt your gun's internals but make sure to wipe down the outside of the gun after you shoot in any condition to protect against rust. Variation in temperature can cause condensation on the gun and can affect your poi (point of impact) if you shoot with a scope since the glass inside your scope (lenses) will expand and contract.
You've asked some good questions but this is an old article (2006) and not many people check back here for new comments. I would encourage you to move your questions or retype them on the current/active comments section. Lot of great airgunners there asking & answering questions of one another. Maybe someone on the current blog has an 850 and help you more than I did. Here's a link that will take you there:
/blog//
Look forward to hearing from you on the current blog.
kevin
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thax kevin..helps a lot
myles
Very interesting article! But what about distance, how far can a pellet go?
@ mechredd, there is no documentation of such nonsense other than urban legend, about .50 BMG bullets being lethal without contact, and especially nothing as preposterous as "liquifying brains" at a foot's distance. By now you've probably seen the Mythbuster's episode completely shattering this (rather unspectacular) myth. Even at close range, moving objects closer and closer until nearly grazed by the bullet, they couldn't get the slightest disturbance. Let alone the earth-shattering destruction that the myth purports. Think about the energy the bullet would need to have. To create enough overpressure for that kind of destruction at 1 foot radius, say, over the first 100yd, the bullet would have to shed in the region of half a billion foot-pounds. For a 750gr BMG projectile to have this much energy it would need to be traveling 500,000 fps, which is half the speed of light. Granted, at this speed relativistic effects would come greatly into play and the projectile would increase in apparent mass. Safe to say, it is impossible with the BMG's mere 13,000 ft-lbs energy, of which only a tiny percentage would be shed as air resistance in flight past a human. An average .50 BMG bullet may start with 13000 ft-lbs at 0 yards and shed 11000 ft-lbs over 2000 yards, that's on average, 5.5 ft-lbs energy transferred to the air, every yard of travel. At 1 foot distant from the bullet's travel, the pressure wave is dissipated by a factor of nearly 50. Let's say one square foot of the pressure wave impacts a (helmeted) soldier's head. He receives less than 0.3 ft-lbs of energy distributed over the whole head. That's the equivalent of dropping 5oz from a height of 1 foot, onto a cushion on his head. Barely a breath of air. No liquified brains. Even an exposed brain would just feel a tickle, and laugh. Unfortunately in this real world, we must hit the target and hit the kill zone.