Archive for December 2008

Understanding the performance/power curve of a PCP

by B.B. Pelletier

This final blog of 2008 was inspired by several questions from reader Kevin but also from other readers who are now owners of precharged pneumatic (PCP) airguns. I’ve written these things before, but perhaps never put them in the same order as I will today.

A PCP valve operates best between a certain high and low pressure point. That is to say the valve will open and remain open long enough to pass air from the reservoir to power a pellet to more or less the same velocity. When the reservoir pressure is high, it acts on the valve to close it faster, but the air that passes through the valve when the gun fires is under a lot of pressure. As you continue to shoot and the reservoir pressure drops, it acts with less force and less quickly on the valve to close it, so the valve remains open slightly longer. The air that passes through the valve before it closes is not pressurized as high; but since the valve remains open slightly longer, it delivers similar acceleration to the pellet. The result is that the pellet stays at the same velocity, more or less, throughout a number of shots.

The string of shots that are at the same velocity are the power curve of the gun. If the reservoir pressure is above the pressure at which this power curve begins, the shots will be slower. If the reservoir pressure is below the pressure at which the power curve ends, the shots will also be slower.

On either end of the power curve–before the curve begins (pressure too high) or after it ends (pressure too low), the pellets will exit the muzzle at a lower velocity than when the valve is dealing with pressure that’s inside the power curve.

As a gun that has been over-pressurized is fired, it loses some pressure with each shot. The pellets will come out progressively faster as the pressure drops, and you can actually record this if you have a chronograph. Then, at some point the velocity seems to stabilize at a level of similar velocities for several shots. That area is the right pressure for your valve and therefore for your gun. We call that area the power curve because it represents the place within the whole pressure curve (zero psi to the maximum fill pressure) at which the rifle operates the best–and also at the same power (more or less).

As you continue to shoot and the pressure in the air reservoir drops below the ideal operating pressure, the velocity of the pellets starts dropping below the ideal range. The decline can be either a straight decline with each new shot or the velocity can go up and down, but it’s always headed in a general downward direction. A powerful gun like the Career Infinity will usually drop velocity straight down with every shot when it falls off the power curve, while a less powerful gun like a Benjamin Discovery may have velocities that go up and down; but the general direction will always be down from the ideal level (the power curve).

So, with yesterday’s 12-shot string that was continually declining with each new shot, I concluded that the rifle was coming down off the optimum power curve–a curve that would have been even higher than the 3,300 psi I put into the reservoir at the beginning. That’s why I said this in yesterday’s blog:

It seems as if the gun’s maximum fill is still higher than 3,300 psi, but I don’t have the pressure to go there. Nor do I think I would if I could. I’ve seen the walls of the reservoir, and they aren’t that thick. I recommend you do not overfill this rifle, because I don’t think there’s a large margin of safety. I did it to demonstrate that the valve was not yet on the power curve.

Do you understand? My last sentence, “I did it to demonstrate that the valve was not yet on the power curve” refers to pressurizing the reservoir to 3,300 psi after testing the rifle at 3,000 psi. Since each shot declined in velocity with a 3,000 psi fill, I boosted the pressure to demonstrate that the velocity would go even higher. I’d hoped the first couple of shots would be close to the same velocity with the 3,300 psi fill, but you can see that they’re not. Of course, that’s not to say that 3,300 psi isn’t the exact point at which the rifle drops off the power curve, and if I had pressurized the rifle to 3,400 psi I might have gotten those few close shots I was looking for. We’ll never know, because I don’t feel confident pressurizing this rifle any higher.

Kevin also asked why I said this–“the valve cannot function with pellets this heavy.” I was referring to some guns that will never have a power curve with pellets over a certain weight. You didn’t notice it because I didn’t report the shot strings. When I went to the lighter pellets, I got some shots of similar velocities. That was with the power wheel set on the lowest power setting. The rifle is very clearly on the power curve with lighter pellets and a lower power setting.

So, Kevin, the velocities I saw told me that this Infinity was not on the power curve with Eun Jin pellets, but that it was very much on the power curve with both Crosman Premiers and Air Arms Diabolo Field pellets. With the lighter pellets, I manipulated the power adjustment wheel to keep the gun on the power curve longer.

Kevin asked what I meant by a “broad flat spot on a power curve.”┬áIn this case, my answer looks better as a picture:

This is a typical velocity-over-pressure chart for a PCP. You get this by chronographing all the shots in a fill. If they look like this, you’ve captured the power curve, which begins at shot 15 (2600 psi) and ends at shot 27 (2150 psi). Filling this gun beyond 2650 psi is a waste of air, as is shooting after the 13th shot.

And, Kevin–every pressure above 2650 psi with this particular airgun is entering into valve lock.

Now you know it all!

Career Infinity by Shin Sung – Part 3

by B.B. Pelletier

Part 1
Part 2

Let’s look at the Career Infinity velocity. The new inlet seal I showed you yesterday is working fine, and it may turn out to be the fix for this problem. I’ll let you know at the end of the accuracy report, when the gun has been filled many more times.

You may recall that this gun doesn’t shoot the pellets from the cylinders. It pushes them into the breech with a bolt probe, and that’s where they are fired from. That way the long gap from cylinder to breech is a non-issue, as far as accuracy goes. The pellet begins its flight while already in contact with the rifling.

However, there are two observations I will make about the cylinders. First, they do not rotate far enough to align with the bore during the cocking stroke. After cocking, I had to advance the cylinder another half turn to get the pellet chamber aligned with the bore. You know that because the bolt probe won’t align with the chamber in the cylinder, which prevents the sidelever from closing. That held true for both cylinders that came with the gun, and it takes away some of the speed you get from the rifle being a repeater.

The second thing I noticed about the cylinders is that it’s possible to insert them into the receiver backwards, with the tails of the pellet pointed forward. If you do that, the pellets still feed into the barrel and still fire normally. Remember to load the cylinders with the outer spring to the rear.

Cocking is easy enough. It isn’t exactly smooth, but the sidelever allows a powerful hammer spring to be compressed with reasonable effort.

The safety is, thankfully, manual. It’s always there if you need it, but you don’t have to fumble with it if you don’t want to. It’s easy enough to put on and take off with just the trigger finger.

The onboard pressure gauge reads in bar instead of psi. I found the one on the test gun reads about 25 bar low, so 3,000 psi reads as 175 bar instead of 206.

There’s a power adjuster on this rifle. There are four spots on the power wheel located in front of the triggerguard and there are a total of 12 positive click detents from lowest to highest power. Since that presents a lifetime of possibilities, I decided to limit the settings based on the pellet being used and how the air was holding out. With heavyweight Eun Jin pellets, I used the highest setting; with medium-weight Crosman Premiers and Air Arms pellets, I used the lowest setting.

Eun Jin
The Eun Jin pellet weighs 28.4 grains, nominally. With a fresh 3,000 psi fill, I got the following results with the first six shots:

985 fps
986 fps
965 fps
957 fps
949 fps
937 fps

That tells me the rifle is not on the power curve at 3,000 psi. It could also be that the valve cannot function with pellets this heavy. I then filled it to 3,300 psi and got these results:

1017 fps
1011 fps
1001 fps
998 fps
987 fps
979 fps

971 fps
962 fps
952 fps
944 fps
927 fps
924 fps

It seems as if the gun’s maximum fill is still higher than 3,300 psi, but I don’t have the pressure to go there. Nor do I think I would if I could. I’ve seen the walls of the reservoir, and they aren’t that thick. I don’t recommend overfilling this rifle, because I don’t think there’s a large margin of safety. I did it to demonstrate that the valve was not yet on the power curve.

Also, the way the valve is constructed, each shot will decline in velocity. This rifle has no broad flat spot on the power curve, like many PCPs do. However, I wouldn’t shoot it this way if it were my rifle. Instead, I’d use the abundant number of lower-powered shots it offers.

Plenty of good shots at low power
On the lowest power setting, a fresh fill gave 6 strings of 6 shots between 927 f.p.s. and 1068 f.p.s. with 14.3-grain Crosman Premiers and 16-grain Air Arms Diabolo Field pellets. That’s a total of 36 shots at that velocity range on low power from a single 3,000 psi fill. Taking a central 1,000 f.p.s. as the average for the 16-grain Air Arms pellets, that’s 35.5 foot-pounds.

To get the last string, I bumped the power wheel up to the yellow level, which is three-quarters full power on this gun. The shots were still falling off rapidly, as you see here:

996 fps
983 fps
967 fps
954 fps
938 fps
927 fps

Maybe 30 shots is more realistic than 36, but that’s a lot of very powerful shots with what may well turn out to be the most accurate pellets. As a practical hunting gun, you either get 12 shots that average about 60 foot-pounds or 30 shots averaging 36 foot-pounds. That makes the Infinity one heck of a good hunting rifle!

The single-stage trigger breaks after a lot of creep at a light 2 lbs., 10 ozs. The trigger blade is too curved for my taste, but I can’t deny that it’s lighter than the triggers of 99 percent of all unmodified rimfires.

There’s a lot of intrigue to this rifle. Now that the inlet valve has been fixed, we’re going to see what it’s capable of. Next time, we’ll look at accuracy.

Odds and ends Removing the Diana 27 seal & fixing the Infinity inlet seal

by B.B. Pelletier

It’s too cold to shoot CO2 outdoors, so the accuracy test of the Crosman 1088 is postponed until we get some warmer days. So, I thought I’d clean up a couple of jobs that I’m working on and show them to you as I go. First, I removed the leather breech seal from the Diana 27 rifle.

Derrick found an inexpensive set of leather punches for me at Harbor Freight, so I ordered them to use in the Diana 27 breech seal project instead of just carving the seal from a leather belt with a sharp knife. There are nine graduated punches in the set for less than $5, so even with shipping I figured it was well worth the investment. I’ll probably have to trim the seal to final size, but the punches will get me most of the way there.

Today I decided to remove the old seal for you, so you can see what the job looks like. Several months ago, I bought a set of dental picks to use on the Walther Falcon Hunter breech seal I replaced during that test series, and they worked well for this seal, as well.

These picks were inexpensive, and they make handling breech seals easy. On this job, I had to break the seal into pieces and scrape it out of the channel.

Old seal was brittle
The old seal came out in chunks instead of a whole seal. That happens only
when the leather has lost all its sealing properties and has transformed into a waxy mass of dark stuff. It should have hung together, but the leather was shot. That happens when there’s no lubrication for a long time–maybe decades.

When the old leather seal is completely removed from the Diana 27 breech, you can see the groove the new seal must fit. This photo is like an Escher print until you decode it in your mind. We’re looking at a breech that’s pointing up–away from us. The groove for the seal is wide and flat and there is a stub of the barrel in the middle. Notice that this shot shows more of the rifling, though a couple lands and grooves at 9 o’clock are invisible.

Weihrauch breech seal possible
Just for fun, I pressed a Weihrauch synthetic breech seal into the groove and it fit. It’s about double the height it has to be for this gun, so I would have to divide it in half before installing, but I think it would work. But I want to try to fit a new leather seal to keep the rifle looking vintage.

I cleaned out the breech seal groove with the picks, so the groove is fresh for a new seal. A toothbrush was used to remove the smaller pieces of disintegrated leather.

That project is now on hold until the punches arrive, so I shifted over to the Career Infinity project. You’ll remember that I replaced the inlet seal on my test gun, but then that seal started leaking, too. Boris made a Teflon seal to replace the brass seal holder in the gun.

Boris made the Teflon inlet seal on the left to replace the three-part inlet seal assembly that came with the rifle. Less mass may keep the seal from deforming too much.

The new seal is lighter and moves very smoothly inside the valve body. Being Teflon, it’ll deform and take the exact shape of the valve seat. Hopefully, that’ll fix the problem of the inlet valve dumping all the air after a fill.

When I filled the gun it held perfectly, but it also did that after the last seal replacement. The proof of the fix will be if the seal continues to hold after repeated fills, which I will be doing as we move into the velocity part of the test. Boris thought that the Teflon seal would be so light that it wouldn’t get pushed out of shape like the brass carrier did to the factory seal. We shall see!

Diana 27 – Part 2

by B.B. Pelletier

Part 1

Today we’ll look at my .177 Diana model 27 rifle after the piston seal and breech seal have been soaked in oil. I told you I put petroleum oil down the air transfer port because my gun is a low-powered springer with leather seals. Leather seals need lots of oil to keep them fresh and pliable, and a low-powered springer doesn’t generate enough compression to detonate the oil. So, petroleum-based oil is fine for guns on this category.

The way to know for certain that you’ve oiled the piston seal enough is to move the barrel through the first few inches of cocking and then relax it. Do that several times and listen carefully to the air transfer port. When you can hear a slurping sound coming from the port, the piston seal is soaked with enough oil to rejuvenate it.

My .22-caliber model 27 that I tuned about 10 years ago with lithium grease on the mainspring still slurps when I test it, despite never having been re-oiled all that time. The excess lithium grease has soaked the seal from the back, making that tune a very long lasting one. However, I did use so much grease on the spring that I gave up some power with that rifle. I think when I tune this one I’ll use black tar grease on the mainspring and oil the piston seal conventionally.

When I oiled the leather breech seal on this 27, it started to disintegrate. I took a closeup photo to show you what that looks like. This seal doesn’t look too good to me, but looks can be deceiving. The chronograph test should tell us for certain if the seal still works. I cannot feel a blast of air coming from the breech joint when the rifle fires, which is one test for an air leak. But a chronograph test should be conclusive.

You can see the disintegration of the breech seal in this photo. Bits of leather are sloughing off, leaving pits where there should be a raised surface. An oil spray can be seen rising from the breech with every shot. Even though I can’t feel anything, that oil spray confirms the fact that the breech seal is shot.

I also felt the barrel on this rifle deserved to be cleaned with J-B Non-Embedding Bore Cleaning Compound. Even though the velocity is not high enough for leading to be a problem with any pellet, we don’t know the history of this rifle. If there’s anything in the bore that could hurt velocity or accuracy (probably accuracy more than velocity), I want to clear it out. We’ll start with a fresh new bore.

The bore seemed easy to clean, and there’s a definite choke at the muzzle end. The breech was very dirty. After cleaning, all pellets loaded easier than they did during the first test. Now, let’s see how the velocity is affected after oiling both the piston seal and the breech seal.

Eley Wasps
Before oiling Wasps averaged 444 f.p.s. After oiling and some sloughing of the breech seal, the average is 225 f.p.s. The breech seal is visibly leaking.

RWS Basic
RWS Basic pellets had averaged around 475 f.p;.s. before (they were very bi-modal, so I recorded two averages) and 212 f.p.s. after. The breech seal has failed.

Crosman Premier 7.9-grain pellets averaged 580 before and 321 after. In fact, only RWS Superdomes held anywhere close to their former average of 412 f.p.s., coming in close at 393 f.p.s.

Well, that wasn’t a very big surprise, given the shape of the breech seal. The big question now is what does the piston seal look like. In my experience, leather breech seals fail sooner than piston seals, but we’ll have to tear the rifle apart to know for sure.

The firing behavior has become rougher, which is the piston slamming into the end of the compression chamber because the air is leaking so badly at the breech. I hope I can save the piston seal, but a new breech seal is mandatory.

I adjusted the trigger, which is the rear screw only. The front screw is just a locking screw, and the rear screw controls how crisp and light the trigger pull is. I screwed it down pretty far, which made the second-stage pull very crisp. The drawback is a longer first-stage pull, but there’s no way around it if you want a crisp second stage.

This photo is worth a lot to vintage Diana owners. The rear screw (at right) is down nearly all the way, and the front screw is tight. This gives a model 27 a crisp two-stage pull.

The next report will be either a disassembly of the powerplant or the repair of the breech seal, whichever comes first.

Merry Christmas 2008

by B.B. Pelletier

Merry Christmas!

I was interviewed on the Arizona radio program, America Armed and Free last week. You can listen to that interview here, if you like. It will be available for one more week.

Today I’ll share a couple of my favorite gifts with you, and maybe you readers can let us know what you got. For those who don’t celebrate Christmas, you can either tell us about your most recent acquisition or just sit back and enjoy the party!

The man who has everything
What does Tom Gaylord’s wife give him for Christmas–the man with the entire airgun world at his fingertips? While that’s not entirely true, a lot of people think it is. They think I can have anything I want.

The truth is, I’m a lot like the rest of you. I do get to test a lot of exotic airguns and related stuff, but my own collection is based more on reality.

However, this year I asked for firearm reloading equipment. Now that my wife and I are shooting 100-200 rounds of .45 ACP every month, I can no longer keep up with my Lee 1000 turret press. So I asked for and received a Dillon Square Deal B press that makes 400-500 cartridges an hour without rushing. Instead of three hours of reloading I will now spend one hour at most to get better ammo than ever before! I also got a bunch of accessories that weren’t included in with the press.

Dillon Square Deal B progressive reloading press makes up to 500 cartridges per hour with minimum effort.

Airgun gift?
I didn’t receive any airgun gifts from the family this year, but I did get a peach of an aperture sight from reader Kevin, who wanted me to try it on a Diana 27. I plan to test it for you in a special report, but I wanted to show it to you today, because it is my one airgun gift this year. And isn’t it sweet? My thanks to Kevin for this beautiful sight.

Kevin sent me this beautiful Diana aperture sight that will fit on a Diana model 27. It has a neat feature about it that Diana owners should know about. I will review it for you in detail.

I’m stopping here, but I want you guys to take over and tell us what you got. I’ll be back tomorrow.

Buying a high-pressure air tank – Part 2 1000 posts!

by B.B. Pelletier

Part 1

Today’s post is the thousandth since we began in March 2005. How fitting that it should come on Christmas Eve. Regardless of your religious views, we all owe Pyramyd Air thanks for their gift of this blog that has lasted so long. Let’s hope we’ll still be enjoying it after another thousand reports!

Although Abe asked for this report, I’ve heard from a lot of other readers who had questions and comments about air tanks. I’ll try to address them all today.

Lloyd wants me to tell you that you should buy the largest scuba tank you can afford. He also says to tell the dive shop operator to please fill the tank to the max, because divers are less concerned with pressure than we are. His most important message, though, is to get to know the people at your dive shop. I couldn’t agree more. I’ve seen airgunners ruin their entire PCP arrangement by simply alienating the dive shop personnel. And I’ve gotten many concessions and good treatment because I acted as though the dive shop was doing me a favor–WHICH IT IS. A little civility goes a long way when dealing with an owner/operator, like the guy who runs the dive shop.

Lloyd also asks if dive shops are the only place to get a 4500 psi fill. Well, I think they are the WORST place! I go to a paintball shop, because my dive shop fills me to only 4,000 psi or so. That’s all his air system can produce. Sometimes, you can get a fill from the local fire station. It helps if the firefighters are also airgunners or maybe you take them a couple dozen donuts when you go there. Like I said, some guys can do it and others can’t. Ask yourself, “What would Wayne do?” when you go, and you’ll probably get what you want.

Jony wants me to remind you that a smaller tank at higher pressure is often better than a large tank at lower pressure. The proof of that is the fact that a 2,200 psi tank won’t even give you one fill of your AirForce Talon SS, despite being just as physically large as an 80 cubic foot aluminum tank that gets pressurized to 3,000 psi. In this game, pressure is king, and we either want tanks at higher pressure or guns that shoot at lower pressure. Having both is the best of all.

Pony tanks
A pony tank is a small air tank that divers and rescue workers use for convenience or for emergencies. We used them in the Army when fording rivers in our M60A1 battle tanks, because some of the crew members in the tank were 10 feet under water when the tank was driving across the river bed. If the air snorkel tube collapsed at those times, the driver could drown before he could get out of the tank. So, he used a pony air tank for a five-minute emergency air supply.

Big bore hunters carry carbon-fiber pony tanks to top off their rifles during a hunt. A small tank that fits in a backpack can refill even a large big bore rifle 2-3 times for a total of 6 additional shots. Any big-bore hunter will tell you that six shots is probably more than a day’s supply for big-game.

When I competed in field target, I carried a 13-cubic foot pony tank to top off my Daystate Harrier. That rifle, which filled to 2,650 psi, got three refills from that little 3,000 psi pony tank. Since each fill was good for 24 shots, that was enough for almost 100 shots if you factor in the initial fill. A match typically has only 60 shots, so I was covered.

The Benjamin air tank is an example of a pony tank. Because it works on the Benjamin Discovery rifle which operates at 2,000 psi, it still gives plenty of fills.

Pony tanks have their place in PCP guns, but you don’t want to buy one as your principal source of air.

Mr. B. says a day in the woods requires more shots than a Talon SS air tank can offer (maybe 35-45 shots at full power, depending on the range). Well, Mr. B., that Talon SS tank is actually a pony tank! Why not buy an extra AirForce standard tank? When your first one runs dry, just screw on a new one? That’s how AirForce designed the gun to begin with.

Filling a gun from a tank
Abe asks about the proper way to fill a gun from a scuba tank, and I’ve had several other people ask the same thing. Here’s a report I did on that subject. The first step is to connect the scuba tank to the gun. For this you need a fill adapter. One end connects to the scuba tank, the other connects to the gun. Both have to fit what they connect to, so you have to determine what it takes to do that. Scuba tanks and carbon fiber tanks have all kinds of valves. The most common scuba tank valve in the U.S. in the K-valve, but a DIN valve will sometimes be encountered. When the rated tank pressure goes above 3,000 psi, the DIN valve becomes more common. Your job is to determine what kind of valve your air tank has.

The K-valve is flat with an o-ring to seal it. This type needs a clamp that fits around the back of the valve to hold it.

A DIN valve has a hole with threads to accept any devices. This is the deeper 300-bar DIN hole, though both have the same diameter and threads.

A refill clamp fits around the K-valve.

Abe also asked about the scuba tank inspection process. That’s not a part of this report, but I covered it here and also here.

Buying used
Sooner or later, it’ll dawn on you that a used scuba tank would be cheaper than a new one. But what you don’t know is that there’s a very good reason for that. A scuba tank must pass a hydrostatic pressure test every five years. When they fail or when they get near the end of their useful life, they aren’t worth buying. We had a reader who bought a used tank for $50, then had to spend $135 getting it back in shape. While that was a little extreme (he needed a new K-valve), a hydro and the other tests you need could easily cost $60. And you could wind up with a tank that fails its hydro, leaving you with nothing, because the testing facility will drill a hole in your tank to remove it from the market.

The best way to buy used is to buy from a dive shop you do business with. If there’s a problem, they’ll take care of you.

Diana 27 – Part 1

by B.B. Pelletier

Diana model 27 is a classic breakbarrel. My new one is a .177.

Kevin prompted this report by asking me about the Diana 27 I bought at this year’s Roanoke airgun show. Then he surprised me with the gift of a very nice peep sight made for the Diana model 75. It also works great on the little Diana 27 rifles, and Kevin wanted me to see that so he sent one.

What I plan to do is test my new .177-caliber model 27 and then install the peep sight and test that for you. Unfortunately, the 27 I got in Roanoke doesn’t have a rear sight base for this sight; I’ll install it on my other 27, which is a Hy-Score 807 in .22 caliber. For those who are fascinated by coincidences, the .22 caliber Hy-Score was purchased from the same dealer from whom I bought the .177 15 years before. It was made in August of 1967, while the new gun was made in March of that same year. Spooky, no?

The new Diana came without a rear sight rail. The presence of the Diana logo indicates there never was one.

Many Diana 27 rifles, including this Hy-Score 807, have a rear rail like this for mounting a peep sight.

The top of the rail is textured with cross-slots that assist the peep sight by providing a solid anchoring surface.

I’ll test the new rifle before lubricating the piston seal and again after a good oil soak. The oil will be applied through the air transfer port, so no disassembly is required.

However, I thought this new rifle would also be the perfect one to tune for you so I can show you the inside parts and how I tune it. That’s coming some time in the future.

Before oiling
But right now, we’ll test the rifle as I got it. The 27 is a low-powered spring-piston breakbarrel that was considered medium-powered in its day. The rifle had a long life, starting in 1910 and running off and on until 1986. However, all those model 27 rifles were not the same model. In fact, you can’t really call them the same gun. The model 27 we’re examining here started some time after World War II and finished in ’86. That said, the final pre-war 27 rifle was quite similar in appearance to the post-war gun and differed only in the trigger and a few small details. This particular rifle I’m testing was manufactured in March 1967 (from the date stamp on the spring tube).

Eley Wasps
Kevin also sent along a tin of .177 Eley Wasps for me to test. He says they’re very accurate in his 27, and he wanted me to try them in mine. The .177 Wasp is a domed pellet that weighs 8.1 grains on average. It’s a pure lead pellet. In .22 caliber, the Wasp is also sold in an oversized 5.6mm, but in .177 the head diameter is 0.174″ and the skirt is approximately 0.181″ to 0.183″. I say approximately because these pellets vary a lot. Being pure lead, they deform when handled.

They fit the breech of this rifle very tight and had to be pushed into the bore with a Bic pen to avoid damage to the skirt when the breech was closed. If I didn’t seat them, the velocity was 278 f.p.s. Seated they had a velocity of 444, but it was sharply bi-modal with the lower average at 436 and the high at 460. There was no shot recorded between the velocities of 439 f.p.s. and 456 f.p.s. I suspect an extremely dry piston and breech seal.

RWS Diabolo Basic
RWS Diabolo Basic pellets were even more sharply bi-modal than the Wasps, with a low average of 457 f.p.s. and a high average of 512 f.p.s. No shot was recorded between 460 f.p.s. and 505 f.p.s. These pellets were also tight in the breech and had to be pushed into the bore with a Bic.

RWS Superdome
The RWS Superdome was not bi-modal and averaged 412 f.p.s. The high was 425 and the low was 395. They were also tight and seated in the bore with the pen.

Crosman Premier 7.9-grain
Crosman Premier 7.9-grain pellets could be seated by finger pressure alone. And they averaged 580 f.p.s., with a spread from 560 to 593. On paper, they appear to be a promising pellet, but the target will tell.

I had the feeling after this testing that the leather piston seal and breech seal need copious amounts of oil. So, I oiled the piston seal through the transfer port and the breech seal topically. I’ll repeat this process one more time and give the rifle a couple days to soak it all in. Then, I expect the results to be faster and more uniform.

We shall see!

Top-notch springer
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