The single stroke pneumatic
by Tom Gaylord
Writing as B.B. Pelletier
This report covers:
- What is a single stroke pneumatic?
- The pump head is critical
- Quick fix
- How much power?
- More power
- Low-cost plinkers
- Great single stroke
This report was requested by reader Chris USA, and I expect it will be helpful for a number of other readers, as well. Today we’re going to talk about the single-stroke pneumatic, which was the most recent airgun powerplant to be developed. As far as I can determine, the first commercially successful single stroke was the Walther LP2 pistol that was offered in 1967. That pistol’s name tells us a couple things. Was there an LP1? Probably, but I find no record of it in the literature. That tells me it probably wasn’t sold commercially, or if it was, it was withdrawn and replaced by the LP2 soon after launch. So Walther probably developed the single stroke design in the early 1960s or even the late ’50s.
What is a single stroke pneumatic?
You are familiar with multi-pump pneumatics that use a pump attached to the gun to fill an onboard reservoir with compressed air. When the gun fires, all the air is released with the shot, though there have been multi-pumps that could shoot several times on one charge of air.
A single stroke pneumatic is also a pneumatic, but it will not accept more than one pump stroke. Instead of an onboard reservoir, it has a chamber that the pump head slides inside. When the gun is pumped, the pump head compresses air in this chamber. The pump head holds the pressurized air inside the chamber — there is no inlet valve like you would find on the reservoir of a multi-pump. If you were to open the pump handle for a second stroke, it would fly open from the force of the pressurized air inside, and all the compressed air from the first stroke would be released.
The pump head is critical
The pump head is critical to the operation of a single stroke. It is flexible, so when the gun is pumped, the compressed air in front of the head squashes the sides of the head outward to seal the compression chamber tightly. This is good, except being flexible, the head cannot hold the compressed air very long. It’s not like the inlet valve of a multi-pump reservoir that uses the air pressure inside the reservoir to help hold the valve shut. Air is constantly trying to escape from the chamber in front of the pump head. That is why most manuals say to not leave a single stroke pumped for longer than 5 minutes.
Oil is critical to the operation of the pump head. I use silicone chamber oil since the guns are pneumatics. The oil improves their sealing and velocity right away.
The pump head may dry out and stiffen over time. When that happens, it won’t flex enough to completely seal the pump chamber and the gun’s velocity will drop. I found a temporary fix for this several years ago that adds velocity to the gun. Simply pump it several times without completing the stroke. In other words, do not put any air into the gun. This will warm the pump head by squashing it repeatedly, putting some flex back into the material. I demonstrated this process on American Airgunner in the 2010 season. I think we got the gun shooting 60 f.p.s. faster with 20 partial pump strokes.
How much power?
What will a single stroke do? The LP2 produced around 350-375 f.p.s. That’s about what a Daisy 747 does. Modern versions of the powerplant can put lightweight lead pellets out of a target pistol muzzle at around 450-500 f.p.s. That’s ideal for a 10-meter target gun. Because of this power level and also because they don’t recoil, single strokes evolved rapidly in the world of target shooting.
Soon after the LP2, Walther brought out the LP3 — a refined version of the earlier pistol with a more reliable exhaust valve. It hit the streets in 1973. No extra power was created; the pistol just became more robust.
A year later Walther brought out the LGR, their first single stroke target rifle. It was so well developed that it lasted from 1974 until 1989. The LGR launched medium weight target pellets at around 575 f.p.s., so it was hotter than the pistol.
Sporting shooters looked at the single stroke with envy and wanted one of their own. The thought of pumping an airgun just once attracted them. But they wanted more power — naturally. What they got, instead, was the Parker Hale Dragon — a science experiment in a stock!
I saw this Parker Hale Dragon at the 2008 Little Rock airgun show. Its operation is quite complex.
First the button is pushed to open the bolt for loading. This keeps the firing valve closed during pumping.
Next, the cocking arm is pulled back and out to unlock it from the action.
Then the cocking arm is rotated about 105 degrees so it is past the muzzle. There is still about a foot more travel to go here. Then the arm is rotated closed and locked in place. The rifle is loaded, the bolt pushed home and locked and the rifle is ready to fire. It’s slightly less work than loading a flintlock rifle!
The physics of a single stroke powerplant do not lend themselves to sporting power. To get everything they have to offer requires a gun that is cumbersome to operate and expensive to make.
So, sporting guns are out, but target guns are definitely in. Daisy has had the model 853 and its variants in their lineup for the past 31 years. The first one was built in 1984. At one time this one rifle dominated NRA Sporter Class marksmanship programs until other manufacturers realized what a plum they were missing. Over one million shooters participate in the NRA/CMP programs each year.
The 853 features a Lothar Walther barrel and can hold some respectable groups, owing to the lack of recoil. The trigger is a bit heavy, but coaches have discovered ways of improving it so it meets the required specifications and still breaks cleanly.
Best of all, the 853 is affordable. New airgunners may be put off by the price, but anyone who shoots 10-meter competition knows what a bargain it really is.
Another type of single stroke is the low-cost plinker. Daisy makes guns like their 845 Mentor and Gamo came out this year with their new Cadet. Both rifles shoot either BBs or pellets. The best thing they have going for them is the easy pump effort. Airguns like this make far better choices for younger shooters than heavier more expensive multi-pumps like the Benjamin 397.
Great single strokes
In the late ’90s the Russians started exporting their IZH 46M target pistol. Well, it was just the 46 in those days. They stretched the compression chamber and boosted the power to 500 f.p.s. to create the M. What makes this gun so neat is its pump linkage. It has a moving fulcrum bearing to keep the effort under control. When your hands are in the best place for strength, the pistol reaches its maximum effort.
That’s wonderful but it’s not what makes this gun so great. The greatness comes when you realize this is a pistol that can compete at the regional level against target pistols costing three times as much. The adjustable trigger is very good and the sights are exactly what you need to compete.
If there is a drawback it’s the weight of the pistol. Today’s target pistols all weigh around 1,000 grams or less. This one weighs 3 grams shy of 1300! That’s too much for for most shooters. But if you want a wonderful target pistol and don’t plan to compete — I can’t think of a better gun.
While I have been writing this report the FedEx man dropped a box on my doorstep. Inside was a Gamo Compact — another wonderful value in a single stroke. I plan to start testing that one soon. It weighs just 885 grams, so nearly anybody can shoot it!
I competed with the IZH46 for about a year before buying a Chameleon CO2 target pistol that was my go-to gun for the rest of the time I shot in NRA matches. I didn’t mind the weight of the Russian pistol as much as most folks, but I never did get the trigger to break cleanly at 510 grams. There was always a tiny bit of creep in stage two. Still, most shooters have never used a trigger as good as this one, and it may take some time before they notice anything but a smooth light release.
There you go, Chris. Single strokes are good for target guns and for low-cost plinkers — not for hunting. Keep them well-oiled and they will last a long time. If they ever start slowing down, you now know what to do!