Canadian Airgun Forum

Yep - you read that right - this experimental LGR is shooting JSB 8.44 grain pellets at 732 FPS, producing 10.04 FPE.
Using RWS Hobby pellets, at 7.0 grains, velocity will hit in excess of 755 FPS, producing around 8.9 FPE.



This project began several months back, when a friend offered me a beater LGR action at a very good price. I now had the "test mule" that I had been looking for, to try a concept that had been rattling around in my head for a while - a multi-stroke LGR.

First step was to clean the action up, reseal the piston and valve, and ensure that the gun was fully operational in OEM form. Next, it was a matter of coming up with a valve body design to house a check valve, that would be fastened at the front of the compression chamber. The check valve is a simple ball-check, seating on a 90 DU o-ring. The valve body is held in place by three capscrews with the heads in shear, at three equidistant points in the chamber. An o-ring at the face of the valve body, and another at the OD of the valve body seals the new valve unit in place.



Next, the piston had to be shortened by an amount equivalent to the thickness of the check valve body, which is 0.500". This particular action had one of the older, solid aluminum pistons, so shortening the forward end of the piston, and re-setting the seal into it was not a problem.

The completed multi-stroke LGR action has but one tell-tale sign of having been modified, and that is the single capscrew head showing, just behind the breech area. The remaining two capscrews are hidden within the stock.



The moment of truth - will it work???
Whoopee !!! It worked !!! Two pumps resulted in a pretty good blast of air, so on to the chrony test bench. I was a bit concerned that the combination of the shortened stroke, and the slightly larger headspace area created by the addition of the check valve unit might have reduced the velocity produced by a single stroke of the lever to an unacceptable level, but that was not the case - I had lost approximately 40 - 45 FPS, so the gun is still shooting at over 500 FPS on a single stroke of the lever.

After testing with a few different brands and types of pellets, the best results were achieved with the trusty JSB Exacts, in 4.53 dia. and 8.44 grains.

Taking the average of a ten shot group at each power level netted me the following numbers:

1 stroke - 509 FPS.
2 strokes - 644 FPS.
3 strokes - 700 FPS.
4 strokes - 732 FPS.

The pumping effort isn't bad at all, but the 4th stroke does start getting a bit difficult. I tried 5 strokes to see where that would take me, and what I ran into there was valve lock - the LGR hammer mechanism did not have the energy to open the valve fully, resulting in only a partial discharge, and leaving residual air in the valve.

The hammer on the LGR does not work in the same manner as that of a more conventional hammer discharged system. On the LGR, the valve stem is depressed through a lever system, which in turn is operated by the hammer wedging it's way under the lever. A very positive and efficient system for the pressure that it was designed to exhaust - but I suspect that the pressure produced by 5 strokes of the lever is possibly several hundred PSI higher than normal, and the OEM hammerspring just lacks the power to drive the wedge far enough for full discharge.

From the numbers noted above, the actual return in velocity per stroke leaves me wondering just how little might be gained by over stressing the components (and the shooter) to get a 5th stroke into the valve - it may, perhaps hit 750 FPS with the 8.44 JSBs, but could also cause premature failure of some part of the gun.

For the moment, I will call this experiment a success - I achieved what I set out to do, and that was basically to get the LGR to operate in a multi-stroke fashion, and to try to meet or exceed 750 FPS.

Very well done and creative conversion Supr! I did a double take when I saw "Walther LGR" and "10fpe" in the same line. I can see that being a pretty nice FT rig

I don't actually understand 1/2 of the technical stuff but it sure is an interesting project!!! Can't dispute the numbers!! You da man, Suprmatic!!!!

with all the people that have been wanting to put more kick into their daisy 953 853, could a similar mod work on one of those platforms? i hear about people wanting to add a hundred or so fps to those things on a daily basis now. likely too much work for a value gun though id guess.

Most the Daisy pneumatic airguns that I am familiar with use a lot of pot metal in the cocking mechanisms and the valve body and securing parts. As such, I do not think that they would be a good candidate for a modification that would over-stress these parts. That of course is only my opinion, but if you can lay your hands on a beater, it would make for an interesting experiment if one were so inclined.

The Walther action on the other hand, is all steel, and over-built - thus, they will stand up to a bit of added stress without worry.

Great job on the build! I didn't think you were affected by the horsepower bug?

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“You don't get anywhere by standing on the sidelines waiting for somebody else to take action.” Please join the CSSA today!

Congrats on a successful mod Suprmatic! ..
Have you had a chance to print some paper with that shooter? ..

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Shoot Safely, Shoot Often & Share Your Sport!...

750 FPS isn't "horsepower", it is an effective FT rifle velocity.

Thanks.
Hope to do some groups with it later today perhaps.

That is really interesting Len, great work as always...

Always cool to see guns turned into a completely different animal, succesfully

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Now, look. It's like this, little britches. All you gotta do is..."Look for the bare necessities...The simple bare necessities...Forget about your worries and your strife"

In the case of this particular gun, it was saved from the dumpster, so the fact that it is even shooting is something of an achievement in itself.

The action had been deemed "unrepairable", and someone did a real number on the valve retaining nut making it near impossible to reseal the valve. The piston seal was almost completely burned away from someone trying to encourage detonation during the compression stroke to obtain higher velocities. The valve was filled with caked on carbon deposits and particles of burnt residue - presumably bits of the piston seal that had been blown away by the detonation.The stock had been broken at the pistol grip, and was poorly repaired with the addition of a 4" long screw from the PG butt right through the vertical section of the PG.

If all works out well with the gun, I will tackle trying to pretty up the stock repair.

Excellent job, Len.... always nice to see a rescue turn out well....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!

Life is too short to be wasted worrying about the opinions of others.

Crazy the things that some guns have been through eh? I love reading your posts on these old victimized guns. Its sad that someone at some point thought they were doing something to help, or they were just fueled by ignorance. But its really great to see them come back to life...

Could you imagine walking into someones shop, there they have a Walther LGR on the bench and they are putting a 4" screw through the stock or pouring some flammable liquid into the compression chamber It would be pretty hard not to scream I think

Great post...

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Now, look. It's like this, little britches. All you gotta do is..."Look for the bare necessities...The simple bare necessities...Forget about your worries and your strife"

Definition of justifiable homocide:

Great work as ever Len. Kudos.

Al