by B.B. Pelletier
Why don’t we wise up?
This discussion seems to beg the question: Why not abandon diabolo pellets and go to bullet-shaped projectiles? Bullets have been around for small-caliber airguns for a decade or more. I’m not advocating their use in this article, but I am making a case for testing the accuracy potential of subsonic versus supersonic diabolo pellets for long-range shooting–before I begin actually shooting.
Before the test is over, I’ll also shoot regular bullets, but that limits the selection of airguns to only the most powerful because they’re the only ones that can stabilize heavy bullets properly. I don’t want to rule out the other air rifles in my quest for accuracy. Besides, a Career 707 shooting a 30-grain bullet at 900 f.p.s. sounds suspiciously like a .22 short standard speed. If I want a gun to shoot like a rimfire, that’s what I’ll shoot. This test is to see what PELLET guns can do!
The Whiscombe JW 75 is the perfect testbed rifle for the “velocity destroys accuracy” theory. Transfer port restrictor screws allow me to vary the velocity of any pellet from barely coming out to as fast as it will go. For the pellet we finally selected, that was supersonic. Scope size is limited on this rifle because the barrel tips up for loading, even though it’s cocked by an underlever. Easy access to the breech allows pellet indexing.
The perfect gun for this test
I designed the following test to see if there’s anything to this velocity/accuracy barrier. We own a Whiscombe JW 75 breakbarrel rifle, which seems like the perfect testbed because it’s so easy to adjust the velocity. The air transfer port is threaded to receive a small Allen screw through which a hole is drilled. A small hole passes less air, resulting in lower velocity. A bigger hole equals higher velocity. Take the screw out altogether and you get all the speed the rifle is capable of with that particular pellet. It’s a simple solution to power adjustability, but it’s very effective and you can adjust that hole to within 10 f.p.s. of a particular desired speed for any given pellet.
Our Whiscombe has barrels in all four popular calibers, and they can be changed in just a few minutes. For this test, however, only the .177 will do, because of the tremendous velocity I’m after. At its peak, the Whiscombe is a 20-30 foot-pound rifle, depending on the caliber and pellet used, so I figured it would be perfect for testing a pellet at two speeds in the same barrel. One special restrictor screw is adjusted to deliver 900 f.p.s. or a bit less, while the open port with no restrictor permits as much velocity over 1,000 f.p.s. as the rifle can muster.
Another advantage you get from a Whiscombe powerplant is stability. The extreme variation in velocity is quite low, as long as the pellets are all prepared and handled the same. Some folks think I place too much emphasis on extreme variation in a shot string, but I feel it’s a great indicator of how consistently the rifle is performing. And consistency is what I’m after when I go for tiny groups.
One potential fly in the ointment is the Whiscombe’s Harmonic Optimized Tuning System (HOTS). Several years ago, Whiscombe started offering barrels with an adjustable muzzle weight built in. We ordered the HOTS on all four of our barrels. But what should I do? Adjust the weight for low velocity and again for high velocity? While that sounds easy in theory, it takes a lot of time to accomplish–as much as a whole day per pellet and velocity. I initially decided not to adjust the HOTS at all and let the barrel vibrate where it wanted. You’ll discover what happened–just as I did.
This view is looking down past the raised barrel at the adjustable transfer port, which is in the center of the picture. The port is partially unscrewed for better identification. But while shooting, it must be flush with the rifle so the barrel will clear when it is swung closed. When the screw is removed completely, the entire hole becomes the transfer port. With this system, it’s possible to adjust velocity to within 10 f.p.s.
My test guidelines–making sure we don’t compare apples to oranges
I decided that all pellets should be lubed before shooting, because I didn’t want anyone saying the high-speed pellets were leading the bore. The rifle’s inventor, John Whiscombe, gave us the formula for an oil–Whiscombe honey–to keep his air rifle barrels free from leading, so I decided to use it exclusively in this test.
These two transfer port restrictor screws have been adjusted to different velocities. The screw on the left shoots .177 Crosman 10.5-grain Premiers at 905 f.p.s. and 9.1-grain Chinese domes at 980 f.p.s. The screw on the right shoots 9.1-grain Chinese domes at 869 f.p.s.–perfect for the test! Each screw was hand-adjusted with a diamond needle file and tested over a chronograph. After the first day at the range, I made a third port for 7.9-grain Crosman Premiers.
Another guideline I adopted for this test is one I have wanted to do for a long time–10-shot groups. Back in the 1960s and even earlier, 10-shot groups were the norm in gun reports. Five-shot groups were sometimes shown, but there was a lot of talk about how they weren’t as representative of true accuracy potential at 10 shots. If you go back to the writings of the 19th century, you’ll find 20- and even 50-shot groups being used to back up accuracy claims. From a statistical standpoint, though, 10 shots will give you a pretty good picture of potential. And it is certainly much easier to shoot 10 than 20.
Ever since the first days of the Airgun Letter, I’ve had a running dialog with champion airgun shooter Rodney Boyce [who recently passed away] about the number of shots per group. Never one to complain, Rodney told me he is amazed at the difference in size between 5-shot and 10-shot groups from the same gun on the same day. I agreed with him that 10 are better than 5, but I’ve done nothing about it until now. For this test, I resolved that all test groups would have 10 shots and let the chips fall where they may.
That said, I must impress on those who have never shot at 50 yards with an air rifle that it is not easy! Any puff of wind WILL open your group. That lightweight, relatively slow-moving pellet is just as sensitive as it can be to the movement of air. Why don’t I shoot this indoors? I would like to, but the facilities aren’t available. So, I’ll shoot outdoors and take my lumps. If that means a half-inch rifle starts shooting an inch or more, so be it. There will be no editing here. Because, if you think 50 yards is hard, you ain’t seen nothin’ till you back up to 100! Your “groups” start looking like open shotgun patterns at that range. And 100 yards is where we’re headed. [Note: That 100-yard, long-range test was one I was working toward in The Airgun Letter. I never did the final test.]
I’m not conducting this test to find out how accurate a certain air rifle can be. Who cares what a Whiscombe can do, if everybody doesn’t have one? I’m doing this to learn about general long-range airgun accuracy potential, as it is affected by velocity. Undoubtedly, I will get lucky a time or two, but that should be more than offset by the vagaries of shooting 10 times at the same target. No one is that lucky.
34 thoughts on “Velocity vs. accuracy: Does it REALLY matter? Part 2”
BB: Off Topic. Do you own a Crosman 600? Do you ever plan to do a blog on the gun?
From the 2006 Pyramyd Air archives:
Here's a modification I wrote about for a 600 a month or so ago:
If you have any specific questions, ask away. Several of us here own them.
Sorry to hear you had the stomach flu last weekend! Hope you are completely recovered now.
Glad to hear that your 2250 is fixed! Saw the pictures over on the other forum. That explains why it didn't puncture on the first shot.
So are we eventually going to see a list of the pontentially best velocities to use for a certain pellet or can other factors make that list only good for one air gun?
Sorry I showed up a little late to comment on Post #1 of this topic, but this should prove fun.
I was shooting my Marauder at 100 yards last weekend. On a gusty day – when I was struggling to hold 1" groups at 50 yards with my .22 rimfire – I was shooting 5-shot groups around 3" (.177 JSB Exact Heavies), and while that's hardly world-beating, it is a lot of fun.
A couple guys came over from the handgun range, drawn by the fact that they could hear me hitting the targets, but not any muzzle report.
They were astonished to learn that I was easily hitting shotgun shells at 50 yards with an airgun, which they equated with bb guns.
Long-range precision centerfire shooters spend an inordinate amount of time tweaking their guns and their handloads for max performance at range.
While airguns are limited a bit (we don't get to play with powders, and the barrel you get is the barrel you get), I wonder if the availability of powerful PCP guns won't power a new wave of long-range airgun shooters.
I'm really looking forward to your long-range testing, and wondering if it isn't time for the airgun sports to loosen the straitjacket just a bit.
I would think the Air Force rifles, especially the Condor, would make for a better test platform with their power adjustability and lack of recoil. Is the power adjustment less calibrated?
Trout Underground, 3 inches at 100 yards is another eye opener for me. That's probably better than a lot of centerfire groups that are shot. And it seems that 100 yards is the limit of most shooting ranges anyway; it's the most I've encountered. How many have access to greater distances?
Actually that reference to a long-range test was from an article I wrote over eight years ago. It's not a part of my current plant.
However, I see the inevitability of it.
I have 200 yards on my range–but let's not go there just yet, shall we? One-hundred is plenty challenging.
The Whiscombe is quite a bit more precise when trying to achieve velocities. However, It can be done with the Condor as well. The Condor simply was not yet in the picture when I wrote this article in 2001.
BB are you going to shoot with unsorted and weight sorted pellets at 100 yards? In my experience in shooting at 100+ yards no matter how good the rifle or shooter is the pellets needed to be sorted for better accuracy and round groups instead of vertical strings. I have been shooting at long range a lot with my Talon (18inch barrel) this year,maybe I could do a guest blog if I do some more shooting and and testing?
I was thinking the same thing about the Airforce rifles but as BB said the Wiscombe has more precise adjustments. My local range has a 200 yard range but I don't go very much do to packing and driving.
I have shot several MOA groups out to 100 yards with my Talon from a sitting position. They were shot on perfect days and I could only shoot them about 20-25% of the time I am shooting groups at long range. I can not say ok this group will be 1 inch or less at 100 yards like I can shooting at 50 or 60 yards.
Jeff in Ohio
Anyone have a link for a Daisy 953 assembly drawing.
Have mods done and am putting it back together and an assembly drawing might be nice.
Here's one with lots of pictures and info:
Once again, this report is copied from The Airgun Letter and is 8 years old. I have no current plans for a 100-yard test. However, I can see it coming.
I will use every trick in the book to shoot well at that distance.
Thank you for the link and prompt reply.
But I'm looking for a factory assembly drawing. You'd think Daisy would have them like Crosman does. But.. couldn't find it if they do.
BB, for part three, you should post right at the beginning in bold that this is an article from 2001, and not a new test.
Though the black and white pictures could be a tip-off.
chris in colorado (the guy that took the pictures that I linked you to) has the factory diagrams/exploded views and has emailed them to folks like you in the past. Contact him.
AF rifles are a very poor and dificult rifle for these kinds of tests for many reasons. Just controlling the the velocity for more than a few shots requires considerable tuning.
Let me give you an example of how setting the power wheel for a steady velocity DOES NOT work.
Yesterday I was shooting my Talon 18" .22 with Kodiaks, condor valve, and a TT 96 gm hammer.
Started with a PW setting that was giving me MV around 960 fps.
MV slowly creeped up for a few shots, then began creeping MUCH faster….
over 1000 fps and heading up fast.
over 1100 fps and heading up fast.
almost hit 1200 fps before the muzzle blast knocked the cover crooked on the chrono and allowed a light reflection to clock a kodiak at 3000+ fps….serious error!!!
I also shot through my duct seal pellet trap. Through the duct seal, the steel backing plate in the trap, the wooden back of the trap, and the dry wall on my basement wall.
AF rifles can be very touchy for many reasons besides the lack of ability to maintain any particular mv.
DB This helped wtih my 953
the pics at scribd are good Kevin…
DB direct link:
wow that could have been a video…
you get a 953 that shoots well with a good triggger mod and it's hard to any better for the money.
Lucky guys with your 200 yard ranges. I'd heard that the power adjustment on the Air Force rifles was an approximation. All the more impressive to shoot MOA 25% of the time at 100 yards. I doubt that most rimfires could do that or even centerfire, and I thought the Talon was handicapped by its light weight.
B.B., I have been most intrigued by the accuracy of your SKS and have looked into it. Apart from exceptions, the un-scientific internet consensus seems to place the SKS on a level with the mini-14 which is not renowned for accuracy. Have you encountered other accurate SKS's? Maybe you got an especially good one.
It is more than light weight that works against stability for AF rifles as opposed to the heavier competition rifles. Ergonomics make them very difficult. They are the strangest and most unnatural feeling guns I have ever shot.
If you tune them up right and use them within their optimum performance range with the best pellet that they are tuned for, they can show some very good results…if you can adapt to the ergonomics problems.
There's something new…now you can share your own images link next to the PA airgun ad pictures.
I have owned two Mini 14s and at least three SKS and I can tell you from that experience that the SKS is more accurate than the Mini 14. The new Mini 14 is probably different, as Ruger has taken steps to improve the accuracy, but the old one is a six MOA rifle at its best–at least in my experience.
My current SKS is the most accurate one I have owned, but in fairness to the other two, I never shot them at paper. They were plinkers, because I owned them at a time when ammo was very hard to come by. (the 1970s).
I would say the Mini 14 is more on a par with the M1 Carbine than with the SKS. But you know, I could be completely mistaken.
One reason I think I am right is the Mini 14 sights are very sloppy, and the SKS sights aren't. I bet a gunsmith could tighten one up a lot just by fixing the sights.
That's my experience.
I've been testing a few of my newer acquisitions at 60 yards using Crosman Premier Light's (my standard pellet), when I decided to do some side-by-side comparisons with the the Premier HP's of the same weight. With the three higher-powered springers I've tried so far – a Beeman R10, an RWS 52, and a Beeman 250 (Diana 45) there seems to be no perceptible difference in group sizes. Granted, I'm not shooting killer groups – but if the domed Premier really tended to by much more accurate than the HP, I'd expect my 10 shot groups to show it. Also – the POI doesn't change much, even though I would have expected the HP to drop more because of poorer aerodynamics leading to faster velocity loss and longer flight times. But this doesn't seem to be the case to any significant extent.
Anyone else ever try shooting them side-by-side?
I've got to get some of those crosman hp's. I've read that a lot of guns love them and they're cheap.
Alright I've been patient long enough.
Did you get the gun you were stalking on gunbroker over the weekend? Are you ready to tell us what this coveted springer is that is more worthy than your pw tuned springers (including that fantastic black and nickel hw30)?
Kev, it's not just that 'a lot of guns love them'. I'm wondering if they're going to prove to be almost interchangeable with the more expensive boxed Premiers – in that if a gun works well with one, it will automatically work well with the other.
I was at a sportsman warehouse the other day and looked for them. Pathetic selection of pellets. Pyramyd Air has spoiled me.
I hear a lot of people buy them at wally world. Your endorsement has pushed me over the edge. I need to find a tin and try them in a couple guns I have that like the premiers.
I was not successful in my pursuit of the rifle on Gunbroker. However I was fortunate enough to correspond with a member of one of the forums who is going to send a freshly tuned version of the rifle I wanted shortly. I have to say he is a credit to the hobby and true gentleman.
I would like to clarify that all my tuned rifles were wonderful, whether from Paul or Rich. I did not part with then due to any short comings. It’s just that my current position and for the foreseeable future was to stop collecting and just have a single PCP in .22 and a Springer in .177. As you are aware, the PCP is the FX Cyclone. I am not saying it is the ultimate in PCP’s, just that it fills all my particular needs extremely well.
So the same theory goes for the Springer. Some of the ones I considered like the Beeman R-8, I never had the slightest interest in before. My requirements are very different now that the muscle is covered by the Cyclone. I don’t need any more power than the HW-30, but I do want a larger size. But not too heavy. I covet accuracy, a nice trigger and a quiet discharge. I also want something that I never had before and that has a classic look in contrast to the modern end the PCP fills. This rifle will mostly be used in doors at ten meters or for plinking. Given my exacting needs, I doubt few others would have an interest in it.
More important than what I chose, if what do you think it is? You’re relatively new to the sport, but you have gained knowledge at a swift pace. Given your vast firearms experience it is no wonder your expert status was achieved so quickly. So what would you recommend?
Finally, until I receive it and shoot it I may be wrong – again. : )
Kevin & Ajvenom,
Thanks for the links and help.
Daisy emailed me an assy diagram. Should have done that first. Anyway 953 is back together and shoots.
Power mod seems to have worked. Lighting was too bright this afternoon so I didn't use the Chrony… but it seems to be shooting harder. Meaning it now can has less drop at 30-yards.
Trigger mod… not so impressed. Think I go back in and add the screw on the link. Seems like both screws could co-exist and server intirely different functions.
Will let you know. Maybe next week.
While I haven't done any real testing, I've noticed that Premiers and Premier HP shoot about the same, too.
I cast my vote for an FWB 124 tuned with a Maccari kit. You'll get exactly what you want.
The trigger can be set very nice, but it will be the hardest part to do. IU would let a noted airgunsmith do the job, if I were you.
You'll have velocity in the mid-800s, light weight, great accuracy and a smooth-shooting airgun.
I was in New Hampshire for vacation, and bought two new rifles from one of the big flea markets. The first is a Mossberg 151M(a), semi-auto .22, with all the original sights, and the other is a pre-war Diana Model 22.
The Diana seems to be 100% complete and perfectly sighted in at short range. At $60 bucks, I never put it down for fear someone else would grab it off the table. I seem to remember a blog about the Model 22 a few months ago, but haven’t searched for it yet. Just like the blog said, this one is low power, easy to cock and quite accurate (I was shooting plant stems at about 10 paces.) I think I have the perfect apartment gun !!!
Perra Dog ,
I didn't do the Diana 22, but I did do a couple of Czech Slavia rifles that are very much the same thing.
You were wise to grab that rifle.
Daystate has a newer pellet designed specifically for better accuracy in crosswinds. Saw a report on it but can't find the link again. Can you check on it and do a test? Really sounds promising. Not great but OK in still conditions but much better than others in gusty and windy conditions and at longer ranges.
Give me a name, please.