Posts Tagged ‘precharged pneumatic’
by Tom Gaylord, a.k.a. B.B. Pelletier
This report addresses:
• What is a pneumatic?
• No. 1 lubrication need.
• A short pneumatic history.
• Which oil to use?
• Other lubrication.
• Wipe down.
This report was written for blog reader Joe, who asked for it specifically; but I know that many of our newer readers also found the information useful. Today, we’ll look at pneumatic guns. There are 3 very different types of pneumatic airguns — precharged, single-stroke and multi-pump — but I think they’re similar enough to cover all of them in the same report.
What is a pneumatic?
Pneumatic airguns store compressed air for one or more shots. Single-strokes get just one shot per fill and so do most multi-pumps, though there are some that do get multiple shots. Precharged pneumatics (we shorten the name to PCP) get many shots per fill.
Big bores, which are always PCPs, get the fewest number of shots per fill, but the smallbores (.177, .20, .22 and .25) get many. How many depends on the output power of the gun and the amount of compressed air that’s available (i.e., the capacity of the air reservoir).
No. 1 lubrication need
The most important reason to lubricate a pneumatic of any kind is to seal the gun. This is similar to gas (CO2) guns; but since pneumatics use air — which is thinner than CO2, their lubrication is extremely important. The seals in the guns are all sized to their jobs. In the case of o-rings, they sit in channels that assist in their sealing role; but without the right lubrication, all would be lost.
A short pneumatic history
Pneumatics are the oldest type of airgun, and their technology has evolved over more than five centuries. The first pneumatic guns used leather seals in all places to seal the reservoir as well as sealing the firing valve.
As time advanced, airgun makers learned how to lap (polish until smooth) valve faces of animal horn that is much better and less porous than leather. These valve faces would be hand-lapped to match the exact surface of the metal (brass or bronze) valve seats to which they were fitted. When the lapping job was finished, these valves would hold air much longer than leather. Leather was still used to seal the junction around the threads of the reservoir, so the guns still leaked down — but the amount of leakage was reduced by a significant amount.
[Note: Airgun designer John Bowkett determined decades ago that precisely machined stainless steel valve faces and valve seats work best of all, providing there's enough lubrication and the machining is correct. The contact surface of this type of valve is extremely fine and narrow; but if it's perfect, this valve will be very controllable. The downside is that valves made this way are still extremely labor intensive.]
Leather seals and horn/brass valves were still being used in big bore PCP airguns up through the 1920s. Smallbore PCPs didn’t come into being until 1980, when Daystate converted one of their tranquilizer dart guns into a .22-caliber sporting rifle they called the Huntsman. Daystate was the first company to build a modern PCP; and when they did, synthetic materials were both available and far better suited for pneumatic valves. At the same time, o-rings in properly cut channels provided the remainder of the sealing solution in place of leather — and the modern PCP was born.
Synthetic seals are less porous than animal horn and last far longer. They’re not as hard as stainless steel, so the mating surfaces of the valve do not have to be machined as precisely (they have a little give to accommodate slight imperfections in the valve seats). Synthetics make the modern PCP possible. And lubrication is what keeps PCPs sealed almost forever.
Leather seals in other pneumatics
Leather has been used for the peripheral seals in multi-pump pneumatics up to as recently as the 1950s. Just like the leather seals of old, the problem has always been how to keep the leather seals lubricated so they remain soft, pliable and doing their job. Oil was used originally in these airguns in the late 1890s. But times change and today we have better lubricants. Petroleum jelly will stay on the job many times longer than straight oil, so even the leather seals in your vintage multi-pumps can be lubricated for a long time.
Which oil to use?
That brings us to the big question of the day: Which oil to use? In this instance, there isn’t just one answer. For PCPs, the right oil needs to have a very high flashpoint so it isn’t prone to explode when subjected to high pressure.
I know of two instances in which petroleum-based oil or grease has caused an explosion in a PCP. One was a vintage PCP reservoir that was pressurized to around 800 psi. The interior walls of the reservoir were coated with grease to trap any dirt particles that might get in during filling. This is a common practice with such airguns; but this time the person who greased the reservoir used petroleum grease instead of organic-based (animal) grease. The reservoir blew apart at the soldered seam! Fortunately, no one was hurt.
The other instance was one I got from a news story, and the person involved was, unfortunately, killed when his modern PCP reservoir exploded. The article said he had apparently introduced regular household oil into the reservoir.
On the other hand, I’ve safely oiled PCP tanks hundreds of times with a couple drops of Silicone Chamber Oil through the air intake port. I put several drops into the fill port before the gun is filled. When the air blows in, the oil is atomized and gets on all the sealing surfaces inside the reservoir and valves.
The oil to use in a PCP is silicone chamber oil. For single-strokes and multi-pumps, the answer is different. For either of these types of pneumatics I use Crosman Pellgunoil. Neither of these types of pneumatics are pressurized nearly as high as a PCP, and Pellgunoil always does the trick.
Can other oils be used instead of Pellgunoil? Certainly. I’ve used Gamo Air Gun Oil in my single-strokes and multi-pumps for many years. I use it exactly as I do Pellgunoil for single-strokes and multi-pumps, but I do not use it in any PCP guns.
The thing about multi-pumps and single strokes is to keep their pump cups sealed and working well. These are the flexible pump heads that force air into the guns, either one time or several. They tend to get hard over time and lose their ability to seal, but keeping them oiled and in use frequently will prolong their service lives. Not using a pneumatic airgun is what really hurts it.
For normal lubrication of moving parts, both Pellgunoil and Gamo Air Gun oil work fine. So do most gun oils, like Remoil. What you do not want to use is silicone chamber oil for this purpose because it doesn’t have enough surface tension to lubricate properly. Your parts will rub against each other and wear.
As always you can use the lubricating oils to wipe down your gun’s metal and wooden parts, but Ballistol neutralizes acidic fingerprints and lasts on the surface of metal far longer than plain oil. So, it gets my recommendation for this job. It also gets the nod for the insides of all airgun barrels.
Airgun lubrication is important, for the reasons mentioned in this 5-part report. Sealing is the biggest role lubrication performs, in all cases. We’ve looked at some very specific examples of products that should be used for the reasons stated. If you decide to substitute, you do so at your own risk.
by Tom Gaylord, a.k.a. B.B. Pelletier
The PCP is built on a Crosman 2100B chassis.
This report addresses:
• Mounting a scope on the rifle
• Shooting Air Arms Falcon pellets at 25 yards
• Grouping in smaller pressure bands
• Shooting Crosman Premier lites
• Marketing the $100 PCP
This will probably be the final report on the $100 PCP. It’s been an interesting project, and today I’m capping it off with a test at 25 yards with the rifle scoped. I selected a UTG 3-9X40 scope with illuminated reticle and a one-inch tube. This is a wonderful scope for just under $100. It’s smaller size suits the test rifle perfectly.
In the previous report, I shot at 25 yards with open sights, and the best group of 10 I got measured 1.144 inches between centers with RWS Hobby pellets. For some reason, I overlooked Hobbys in today’s test and began with Falcons, which gave a previous group of 1.912 inches.
It took just 2 shots to get on target, and the next 8 went into 0.992 inches. I was filling to 2000 psi and shooting 10 shots between each fill.
The first 8 Falcon pellets went into 0.992 inches at 25 yards.
Next, I refilled the rifle and shot 10 more Falcons. This time, the group was 1.72 inches between centers. That’s better than the group with open sights, but nothing special.
The first 10-shot group with a 2000 psi fill made this 1.72-inch group.
As I shot this group, I thought the last 5 shots went closer than the first 5, so I decided to fill the rifle to 1500 psi and shoot 5 more shots — then repeat, for a 10-shot group. These 10 shots went into 1.373 inches, which is a significant improvement.
On this group, I filled the rifle twice to 1500 psi and shot 5 shots per fill. The group measures 1.373 inches, so it’s a little better than the last one.
But I thought this time that the shots were scattering more than before. So I decided to boost the fill pressure to 1800 psi and shoot just 5, then refill and do it again. This gave me 10 shots in 1.577 inches, which is not an improvement.
This time, I twice filled the gun to 1800 psi and shot 5 rounds with each fill. The group measures 1.577 inches between centers.
At this point, I remembered that this is just a proof-of-concept gun. We aren’t trying to make the final article here — just prove that it works good enough to be worth the effort. I hadn’t yet tried Crosman Premier lites in the scoped rifle, so that was my final group. This time, I filled to 2000 psi.
Ten Premier lites went into 1.607 inches; but the strange thing was that the first 5 went into 0.629 inches, and the second 5 went into 1.098 inches. And the 2 groups are centered in 2 separate places! Clearly, there are tuning issues that have to be addressed with this rifle. But I don’t care about that. As far as I’m concerned, the $100 PCP concept has been proven.
The groups I got aren’t as small as the ones you’re used to seeing from a PCP at 25 yards, but this one will sell for under $100. So, the accuracy is not expected to be world class. And this rifle’s barrel is held in place by Gorilla Tape and a shim of cardboard. Certainly, there’s more to be done to finish the rifle!
The last comment I’ll make is that this rifle is noisy. A barrel shroud would be welcome.
Marketing the $100 PCP
From the responses we’ve gotten and the things I’ve heard while attending airgun events, I know the $100 PCP is worth trying. I realize there’s a marketing plan to be constructed, so I’d like to start the ball rolling with this:
• Keep the velocity with Premier lites to no more than 800 f.p.s.
• Make the reservoir larger and balance the valve to get 20 good shots (730-800 f.p.s.).
• In every way possible, retain the features of the 2100B.
• If the fill pressure can be made even lower, say 1800 psi, that’s better.
• Consider shrouding the barrel.
• Come out with a hand pump that will retail for under $100, but use a Foster fitting on the rifle so any of the current pumps can also be used.
by Tom Gaylord, a.k.a. B.B. Pelletier
The PCP is built on a Crosman 2100B chassis.
I bet that when some people heard about this experiment, they laughed it off. Perhaps that will change now that we have looked at this novel idea 5 different times. I’m learning so much from this series that it’s going to affect my writing for years to come.
I was surprised — again!
Somebody — I don’t remember who — asked me to test the $100 PCP with round lead balls — I guess because the steel BB test turned out so well. So I did. I shot it at 10 meters with .177-caliber Gamo round lead balls. Since I shot with open sights, I didn’t get to see the group after confirming that the first shot hit the paper. Imagine my surprise to see all 10 shots clustered tightly in 0.561 inches!
That got me thinking — a lot! I’ve been doing this experiment so slow that I forget what I’ve done before.
What I thought I would do today was complete this report with a test of the rifle scoped at 25 yards. However, when I mounted the scope, it was very far off line, as in angled to the barrel. Either the grooves on the receiver are off or the scope mount I chose wasn’t grabbing the base correctly.
After missing the target twice at 25 yards, I pulled the scope off the rifle and decided to shoot another test with open sights. I used different pellets than I used in Part 4 so we get to see some different results.
Crosman Premier heavy
The first pellet I tried was the 10.5-grain Crosman Premier heavy. In .177, Premiers come in both lite and heavy, and this is the first time I’ve tested this rifle with the heavy. I would love to tell you these pellets went into a small group, but the truth is that they scattered in a 2.352-inch pattern.
H&N Baracuda Match
Next, I tried 10 H&N Baracuda Match pellets. They made a better group than the Premier heavies, but it still wasn’t worth talking about. Ten pellets went into 2.051 inches at 25 yards.
After looking at the second group, I noticed that it looked like the first group, only a little smaller. Because I always look through the spotting scope after the first shot of every group to make sure I’m on paper, I knew that the first shots of both groups were high and right. It seemed to me that the shots might be spreading out to the left as the pressure in the reservoir dropped; so on group 3, I took a photo after the first 5 shots had been fired.
Finally I tried RWS Superdomes. Including the lead balls I shot at 10 meters, this was the fourth projectile in this test and the seventh diabolo pellet tested at 25 yards in this rifle. The other 3 pellets were documented in part 4.
Ten Superdomes went into 1.528 inches at 25 yards. That was the best group in this test with pellets, but only the third best pellet of the seven that were tested at 25 yards.
As it turned out, the next 5 shots didn’t open the group that much more. So, another theory bit the dust.
The $100 PCP is very accurate at close range, but not as good as the distance increases. Of course, you must remember that the barrel is taped to the reservoir with Gorilla tape, so there’s a lack of precision in the build.
It would still be interesting to see how this rifle behaves when scoped, but I’ll have to find mounts that permit mounting a scope to the integral rail. At this point, I think the $100 PCP is a proven concept. I would really like to see this rifle in production.
by Tom Gaylord, a.k.a. B.B. Pelletier
The $100 PCP is built on a Crosman 2100B chassis.
This test was very interesting! It began last week at my outdoor rifle range. Blog reader GunFun1 asked me to try shooting steel BBs in this gun because it was originally built to handle them (when it was in its Crosman 2100B form). I didn’t want to do it because this rifle launches the first couple shots at over 900 f.p.s., and steel BBs rebound like crazy (You’ll shoot your eye out), but I did relent. Last week, I took this rifle to my outdoor range and stuck a 12-inch Shoot-N-C target on the plywood target backer. I then paced off 10 meters and fired 10 BBs at this target.
I thought the BBs would probably miss the target altogether. I said as much to GunFun1 in my comments a few weeks ago. But they didn’t!
I was wrong about this. Shooting offhand with open sights, I put 10 Daisy Premium Grade steel BBs into 1.56 inches. It was actually 11 BBs. I must have miscounted during shooting. I was astounded! This isn’t just good — it’s great! You don’t shoot BB guns at 10 meters when you’re shooting groups!
Incidentally, all 10 BBs apparently went through the plywood target backer. Of course, there are other bullet holes there, so the wood isn’t always present or at its thickest; still, it shows those BBs are moving!
That got me wondering just how accurate this rifle could be. I decided to shoot from 25 yards with open sights, only. I’ll come back and shoot with an optical sight of some kind, but this test is just open sights.
I filled the gun to 2,000 psi for every 10 shots, including for the BBs shown above. After 10 shots, the gun’s pressure has dropped to 1,000 psi.
Crosman Premier lite
The first group of 10 shots was shot with Crosman Premier lites. Based on the 10-meter results for the last test, and also from where the BBs went, I adjusted the rear sight to the right just a little. After the first shot, I looked through the spotting scope to affirm it hit the target. It did, was high above the bullseye and fairly well-centered left and right. So, I left the sights where they were and fired a second shot. When I looked through the spotting scope, I saw it had gone through the same hole as the first! Wow! That was starting out well!
The first 4 shots all went into the same hole. Then shot 5 went higher for some reason.
After taking the picture of the first 5 shots, I shot the remaining 5 shots. That was informative because all the shots spread out to the left. Having the first 5 shots on record allowed me to see that the second 5 were the ones that actually spread out. The 10-shot group measures 1.358 inches between centers.
Next up were RWS Hobby pellets. They did quite well at 10 meters, but 25 yards is about the maximum distance at which wadcutter pellets hold their accuracy.
I adjusted the rear sight down one notch before shooting this group. Once more, I photographed the target after 5 shots.
Air Arms Falcons
The last pellet I tested was the Air Arms Falcon pellet. This time, the first 5 pellets didn’t seem to do that well. And when we see the final 10-shot group, it isn’t that much larger.
Conclusions so far
This experiment is turning out much better than I had hoped. Not only have we demonstrated that it’s possible to make a precharged pneumatic rifle that can retail for under $100, we’re now showing that it can really perform! Of course, the production gun will get many more shots on a fill than the 10 I’m getting, but I do think the maximum fill pressure should be held to 2,000 psi. That will make it easier to build an affordable hand pump, which Dennis Quackenbush is thinking about right now.
The discharge noise of this rifle is quite loud. I was going to recommend not putting a shroud on the gun, but I’m going to change my mind on that point. The customers for this gun will be suburban shooters who need a quieter air rifle, so some sound dampening is necessary.
The trigger on the rifle is heavy, and I would leave it the way it is. I would also leave the bolt-action exactly the way it is on the 2100B. The same goes for the sights. These are refinements people can pay for on higher-priced PCPs. We want to hold the cost of this gun to less than $100 retail.
I do plan on returning to test this rifle at least one more time with an optical sight. That will show the maximum accuracy potential, although I believe we’ve already seen a good indication of it in this test.
The $100 PCP will never replace the higher-priced PCPs that are already selling. It isn’t supposed to. It’s supposed to provide that entry-level step for those who are curious about precharged airguns and don’t want to spend a fortune to find out. I think it’s a very feasible goal and, quite possibly, a profitable one, as well.
by Tom Gaylord, a.k.a. B.B. Pelletier
The PCP built on a Crosman 2100B chassis.
Today, we’ll start looking at the accuracy of the $100 PCP. This is the test that has concerned me most since we began this experiment. I knew that a Crosman barrel could be very accurate because of the success of the Benjamin Discovery. But the $100 PCP is a job we threw together quickly just to test the concept. And when I say “we,” I mean Dennis Quackenbush, of course. It isn’t fully developed. Will it shoot well or fail miserably? Today, we’ll find out.
Since this is a lash-up job, there’s nothing connecting the barrel to the reservoir. This is a real free-floated barrel, but that’s not a good thing in this case.
I discussed this with Dennis, who advised me to attach the barrel to the reservoir tube with JB Weld. I was concerned that if I didn’t get the barrel fairly straight, problems would crop up when I scope the rifle. The open sights are mounted to the top of the barrel, so they’ll stay aligned at all times; but the scope base is on top of the receiver. The barrel is separate from that, and that could present a problem.
Thankfully, I’m a highly skilled craftsman, as long-time readers of this blog know all too well. My solution was to install a precision shim between the barrel and reservoir to maintain separation, and then to attach the 2 parts with several strips of linear adhesive material.
In other words, I put a piece of cardboard between the barrel and reservoir tube and then wrapped both with Gorilla tape.
Naturally, I don’t expect the blog readers to be capable of skilled work like this. I’m just showing it to you so your repair center will have the information when they do a similar job for you!
Now, it was time to test the rifle. I shot only pellets, of course, and I decided to start at 10 meters with the open sights that came on the rifle. If I was testing a Crosman 2100B, that’s how I’d start.
Right away, I messed up and over-filled the gun on the very first fill. I’m not used to the needle on the gauge stopping at the 2,000 psi mark, so I went over and filled to about 2,300 psi. Thankfully, Dennis over-built this rifle, but I didn’t want to test that aspect! Nevertheless, the rifle was filled without incident, so I fired the first 10 shots.
Crosman Premier lites were the first pellets I shot because this is a Crosman rifle, after all. I’ve found that pellets and airguns made by the same manufacturer often do well together.
The first pellet landed to the right of the bull and about right for elevation. I left it alone and fired shot No. 2. Since the pellets were in the white, I could see them without a spotting scope (this was only 10 meters); and they were landing close to each other. I settled in and completed the first 5 shots.
I was so concerned that the pellets might walk as the pressure dropped in the reservoir that I photographed the first group after just 5 shots. Then, I photographed it again after all 10 shots were fired.
After photographing the first 5 shots I returned to the bench and shot the other 5. When I went downrange to change the target I was surprised to see that the final 5 shots hadn’t enlarged the group at all! This is not a common occurrence, and it made me think that I should re-shoot the Premiers with a correct 2,000 psi fill, just to be sure. But I decided to wait until the end of the test to do it.
The first 10-shot group of Premiers measures 0.726 inches between centers. As noted, that size was reached in the first 5 shots.
After the first group, I adjusted the rear sight to the left, to get the pellets striking inside the bull. Then, I fired the second group with RWS Hobby pellets. After confirming the first pellet did hit in the black, I didn’t look at the target again until going downrange to change it. What I saw was both thrilling and astounding. With open sights, the $100 PCP had put 10 Hobbys into a group that measures 0.534 inches between centers. This isn’t just a good group — it’s a great group when you consider that open sporting sights were used. Granted, I’m only shooting 10 meters here and the group will be larger when the distance increases to 25 yards, but will it be that much larger? I’ll be using a scope, after all. And maybe I haven’t even found the best pellet yet.
After this group, I adjusted the rear sight up one step. Since the next pellet is a heavy one, that would probably keep it is the same place.
H&N Baracuda Match
Although this rifle is producing only 12 foot-pounds of energy, I thought the H&N Baracuda Match pellets might work well. So, I gave them a shot. Ten went into a 0.855-inch group. That’s not terrible; but in light of the others, it’s not as good, either.
Air Arms Falcon pellets
Next up were the Falcon pellets from Air Arms. Ten of them went into 0.683 inches. Since this is a domed pellet, it may group better at long range than the Hobby.
I then shot a final group of Crosman Premier lites — this time with the rifle filled to just 2,000 psi. Ten pellets went into 0.615 inches, making the second-best group of the day, with Hobbys being the best.
The rifle’s pressure dropped about 800 psi for the 10 shots in each group. So the valve is far from optimum at this point. And the reservoir could stand to be a lot larger.
The trigger is the 2100B trigger. While it does have a long pull, I didn’t find that it caused me any problems. I think it should stay as it is.
The rifle cracks much louder than a Benjamin 392 on 8 pumps. Crosman could shroud the barrel, but I’m going to recommend they don’t. I want to keep the price of the gun down below $100. Let the people who buy them figure out how to quiet their guns. They’re going to anyway.
I’m going to address these next comments to Ed Schultz at Crosman. The $100 PCP tests out the way we both thought it would. You can see the shortcuts I took to stabilize the barrel for today’s test. I would want more than 10 good shots from a rifle like this. I would want at least 20 good, accurate shots of 7.9-grain Premiers going at 850 f.p.s., give or take.
I’m going to continue to test the rifle at greater distances, so there are more reports to come. But there’s no longer any doubt that this is a viable airgun.
by Tom Gaylord, a.k.a. B.B. Pelletier
The PCP built on a Crosman 2100B chassis.
Today is Media Day at the range, and I will be shooting many of the new airguns that will be coming out this year, plus a lot of firearms — I hope. Tomorrow the 2014 SHOT Show starts, and there’s a special first-day report all set for you.
Let’s look at the performance of the $100 PCP that big bore airgun maker Dennis Quackenbush created on a Crosman 2100B chassis. I read some comments about the gun in Part 1. Before we get started, I need to address one of them. Some of you say you want a PCP that operates on 100 psi, so you can run it on your shop compressor. Gentlemen — such an airgun doesn’t exist and cannot exist as you envision it. That is simply not enough pressure to push a pellet to the kind of velocities we want. You can shoot t-shirts into the grandstands with that kind of pressure or perhaps run a pneumatic tube delivery system, but not a pellet gun.
I know that the airguns of old used lower pressure than we use today. They got amazing power from 500 to 800 psi. But they weren’t shooting smallbore caliber pellets. They were shooting .40 to .70 caliber round lead balls and they got them up to 450-600 f.p.s. They did that because the area of the projectile is much larger than a .177 pellet, and also because they used very long barrels (30-36 inches).
You can shoot tennis balls with shop air, but not pellets. I did report on a .25-caliber pellet rifle that worked with 800 psi air, but that’s a lot different than 125 psi air. You can’t pressurize air to 800 psi with a shop compressor. So, we’re going to have to confine our research to what is physically possible. I’m not trying to shut you down for thinking outside the box, but this is a very real physical constraint.
On with the test
Today, we’re looking at the velocity of this rifle with air for both pellets and BBs. Pellets are our principal concern, but I’ll test BBs, as well, since they can be used in this airgun.
Dennis told me what the performance curve looked like, but I’m going to approach this as if I know nothing about this gun. Where do I begin? Well, I may not know much about this particular PCP, but I’ve used enough other PCPs that I’m not completely in the dark. I filled the reservoir to 800 psi, as indicated on the gauge of my carbon fiber tank and then started loading Crosman Premier lite pellets and firing through the chronograph.
Okay, the velocity dropped with every shot, so the valve is not on the power curve, yet. It wants to see more air pressure.
Look at the velocity increase from just an additional 200 psi of pressure! That’s an indication that we’re quite far from the power curve. It took 5 shots before the rifle was shooting as slow as in the first string, so that extra 200 psi really added shots.
A word about the next part of the test is appropriate. The gauge on my tank doesn’t show even divisions of pressure as closely as I would like. Instead of adding another 200 psi, I found myself guessing that I added another 300 psi. If I had a more accurate gauge, I could do this with greater control; but it’s all going to turn out in the end. You’ll see.
4…..did not record (DNR)
This was interesting because there wasn’t such a big increase over 1,000 psi as there had been when going from 800 to 1000, despite adding 300 psi rather than 200 psi. It took just 3 shots for the velocity to become equal to the 1,000 psi string (compare shot 3 from this string to the first shot of the previous string). The extra air pressure isn’t doing as much as it did before.
Okay, look at the first 5 shots in this string. See how little velocity they lose compared to the first shots in previous strings? That’s significant. It means the valve is beginning to operate more efficiently at this pressure level. Dennis told me that when he reached 1,800 psi, the rifle stabilized for him, as well. What we don’t know and cannot know for sure is what pressure either Dennis or I actually used because neither of us has a calibrated pressure gauge. We’re just guessing based on the inexpensive small gauges that come with all pressure tanks. But, whatever the exact numbers are, they’re pretty much in the same ballpark.
We have a PCP that operates at 1,800 psi — or so. But when I say “operate,” it isn’t really operating the way we want a PCP to operate. We want to see a nice string of shots that are fairly consistent — some a little higher and some a little lower, but a nice string where the velocity is stable. We don’t have that yet. What we have is a rifle that wants to operate at this fill pressure but probably needs a number of tweaks to get where we want it to be.
There’s one more thing to do. Dennis and I talked about this, and he said if there’s a weakness in this rifle, it’s at the threads where the air reservoir is threaded to the brass valve. While the reservoir is way overbuilt, those threads are a place where not too much more strain can be applied. Dennis feels that it will be safe to 2,000 psi but not much higher. I agreed with him on that, so I did one last test at 2,000 psi.
Okay, adding 200 extra psi increased velocity significantly, plus it also gave us a greater number of consistent shots. I would call the first 7 shots fairly consistent, and the velocity doesn’t really start to plummet until after shot 9. What this tells me is that the valve return spring is way off. It’s probably too heavy. And Dennis has already criticized the valve itself. It’s a poppet shape (looks like a top hat) instead of a valve with angled sides that mate with an angled valve seat.
Add to that an enlargement of the valve port (through which the air flows) that might help lower the operating pressure, and the new valve would handle the pressure better than this stock one that got pressed into service for which it wasn’t designed.
What about BBs?
Okay, I can’t end without giving you some BB velocities. Since the rifle works so well at an indicated 2,000 psi, I decided to skip all the early stuff and go straight to the string we’re all interested in.
For this test, I used Daisy Premium Grade BBs that I know from measurement are both the largest and also the most consistent steel BBs on the American market. Since steel BBs run 0.171 to 0.173 inches in diameter, they’re considerably smaller than .177-caliber lead pellets, no matter what their packages say. BBs are NOT 4.5mm!
Like the pellets with a 2,000 psi fill, the first several shots with BBs are close to each other and after, perhaps, shot 6 or 7, the spread opens up. Of course, you have to realize that steel BBs going over 800 f.p.s. are extremely dangerous. Lead pellets start to disintegrate at velocities above 600 f.p.s.; and at 800 f.p.s., they almost vaporize when they hit a hard target such as metal. But BBs not only hold together, they absorb the energy of the impact and bounce back at nearly the same velocity. Believe me — you don’t want to be hit by one!
What have we learned?
So far, we know this rifle works but is not a fully functional precharged pneumatic because it does not shoot a string of shots at a steady velocity. However, that doesn’t stop us from proceeding with accuracy testing.
What’s been proven by this test is that the idea of a $100 precharged pneumatic rifle is completely plausible. The needed changes have been pointed out; but as we proceed further, no doubt, other things will be revealed. That’s the way of product development.
Remember this is a testbed — not a production rifle. Also remember the rifle that it was built from. We should expect accuracy to be similar to the Crosman 2100B, which is fully acceptable at this price point. And I’m going to select a string of shots whose velocities are relatively close to each other, so I probably won’t be shooting 10-shot groups.
I’ll need to do some things to the gun before starting the accuracy test, but I’ll tell you about those things in the next report.
by Tom Gaylord, a.k.a. B.B. Pelletier
Airgun manufacturers: If you read this blog, today’s report is one you’ll want to pay attention to! When I announced last Friday that I would be writing this, I received more interest than any subject that’s ever been raised on this blog. That makes this a subject of primary importance to anyone who wants to know what the consumer wants.
Blog readers: Many of you have not read or perhaps not understood all that I’ve said about this project. I am therefore going to explain it now in clear terms, so that everybody will know what I’m talking about. This project is a proof of concept. It is not a new airgun that’s about to be built. I don’t know if it will ever be made; and if it is, it probably won’t look like what you’re about to see. This is a single airgun that incorporates the features I’ve envisioned in a PCP that could retail for less than $100. A lot less, if you follow carefully.
The base gun used as the starting point for the project is a Crosman 2100B. That’s a multi-pump pneumatic that has a lot of plastic on it and a soda-straw barrel. It’s one of those dual-ammo rifles that shoots both BBs and pellets but has a rifled bore. As this report is written, Pyramyd Air has them priced at $59.95.
Dennis Quackenbush turned a Crosman 2100B multi-pump into a PCP by adding a reservoir where the pump mechanism used to be.
The forearm tip no longer has anything to attach to. It used to be the anchor for the pump pivot.
To convert the rifle, Dennis had to remove the multi-pump mechanism (pump linkage, pump anchor, pump head and rod and connecting hardware), including the tube that houses it. A steel hydraulic tube was installed in its place. Dennis chose SAE 1026 tubing that’s 0.75″ diameter on the outside and has a wall thickness of 0.083 inches. That gives the tube a burst pressure rating of 14,386 psi — more than enough for this project. In fact, to use Dennis’ words, it’s overkill.
A tube with a thinner wall thickness would have more internal volume, but it would be marginal for the threads that Dennis cut inside the tube to attach to the brass firing valve. Thinner tubing would have to be pinned instead of threaded. It would still work fine and the burst rating would still be many times the expected operating pressure.
To complete the gun, Dennis had to thread the other end to accept a fill nipple. He also had to change the firing valve return spring because the thick-walled tube didn’t allow sufficient clearance for the factory spring.
Cost to build
What are we looking at? The gun costs $60. The new reservoir tube has a nominal cost of $10. The fill nipple has a small cost, along with some other small parts. And Dennis has to get paid for his time to remove the factory parts, thread the new tube on both ends, install the new tube and seal it on both ends. He also had to turn the pump arm that swings into a forearm that attaches to the pressure tube. A special barrel hanger had to be made so he didn’t need to drill and tap holes in the pressure tube. Takes about a minute to write about all the work and maybe 6-8 hours to do it. Do several and you’ll find ways to shorten the time to perhaps 4 hours.
So — those who expect Dennis to go into business making this airgun want him to fork out $75 and spend 4 hours of his time to make $25. Does that seem fair? Of course not! Even if he could cut a deal with Crosman or a distributor to lower his out-of-pocket expenses for the starter rifle, he’s still working for peanuts.
Crosman, on the other hand, could do something like this with great efficiency! They could make small adjustments to the manufacturing process upstream, so this gun wouldn’t cost them any more to build than the 2100B — or if it did cost more, the difference would be quite small.
So, why don’t “they” do it? Well, I expect our comments will provide some answers. For starters there will be those who find plastic on airguns to be poison. No plastic for them! And the soda-straw barrel will also turn them off. What are “they” trying to foist on us? Don’t “they” know that plastic and cheap barrels turn us off?
Well, I’m not doing this project for people who feel that way. This is a precharged airgun that can retail for less than $100, and corners have to be cut. We don’t ever skimp on safety, but performance? Forget performance! You’re going to get a soda-straw barrel and lots of plastic for under $100, and you’ll be happy with it.
Believe it or not, there are a lot of shooters out there who would be thrilled to get a PCP for under $100. They would accept the thin barrel and the plastic, knowing that this is the only way they will ever get close to their goal of an affordable PCP. Those are the ones I’m doing this project for. The others can buy the more expensive PCPs and make all the comparisons they want.
Is such a PCP worth the effort? What kind of velocity will it have? What kind of accuracy? How many good shots will it have per fill? Is it an airgun worth having, or is it just a dream that was poorly executed? We talk about these things on this blog all the time — but today, thanks to Dennis Quackenbush, we actually have one we can test.
I thought you readers would really enjoy the rifling twist-rate test I did this year and last. I published 13 parts of that report; and by the end of it all, I was standing alone in my field, listening to the crickets chirp. I also published the entire test in Shotgun News as a feature article and, while the editor got excited along with me, there were more crickets chirping. It’s clear that I don’t always know what will turn your crank.
However, if the comments that came in when I merely mentioned this test was coming are any indication, many of you are very interested. And now you understand what this is.
This gun has a cheap soda-straw barrel (one made from very thin steel tubing). It’s rifled with a compromise rifling that’s good for both lead pellets and steel BBs. The trigger is the same one that’s on the Crosman 2100B that I tested for you. So, expect accuracy like you saw in that test. It wasn’t that bad, as you will see, if you bother to read that report. As for velocity, well, I already know what it is, but I’m not telling today. That will come in Part 2, like it always does.
The point of this test is to see if a gun can be made this way, and, if it can, how will it perform? I’m not going to tune this rifle to turn it into a viable air rifle, if it isn’t one already. I just want to know if it works. If it does work, does it work good enough that it would be worth building a commercial rifle just like it? In short — is this worthwhile?
I haven’t mentioned numerous things. Things like the fact that larger-diameter tubing could have been used, if the design was altered upstream in the manufacturing process. The cost wouldn’t have been that much more because the alterations would have been made with cost control in mind. Obviously this rifle could also be made as a .22. Is that of interest to anyone? There is a Crosman 2200, you know. A better trigger could be made if there was corporate support for one.
I also haven’t talked about the obvious point that the fill pressure of this gun will be lower than even that of the Benjamin Discovery. Because of that, the wall thickness of the pressure tubing can be much thinner than what’s been used here, meaning a production rifle could hold a lot more air than this one. So, whatever shot count we see here can easily be increased with very little additional cost, if any.
And the valve can be modified by an engineer to work best at the pressure that’s available. The new valve will be different than the one in this test rifle, but it doesn’t need to cost any more money.
In short, I’m testing a concept — not a production air rifle. The final rifle can be so much more than the one I test for you, yet the cost to produce can easily be held in check to ensure that a retail price of less than $100 is entirely possible. I’m tired of being told by airgun companies why something can’t be done, and now Dennis Quackenbush has made it possible that I don’t have to. None of us do.
But this is not a high-quality air rifle that’s made of wood and steel. You can’t build a PCP for under $100 and have those things. This is an air rifle for those guys who want to try out PCPs but don’t want to spend large amounts of money getting them. And also for guys who just don’t have the money to spend — period. That doesn’t mean that it has to be inaccurate — but don’t expect a Lothar Walther barrel. And accept plastic for what it is. You accept it on Glocks — expand your horizons.
This project promises to be quite interesting. It will answer questions I’ve wondered about for close to a decade. Because there’s a real air rifle to test, it will put an end to all the loose discussions and blue-sky dreaming that goes on…because this rifle now exists!
I’ll end with a thought from Dennis. If this rifle is worth making, then a lower-cost hand pump (that would fill only to a lower pressure) would also be extremely good to have. He’s thinking about that one right now.