fl(air) gun - mechanically locked pneumatic cartridge for a 26.5mm flare gun

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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Wed Jan 18, 2023 9:40 am

I thought this deserved a separate thread from the earlier development.


Cartridge with a Polish flare gun from the 1950s based on the Soviet SPSh-44.


Cartridge disassembled, most parts are machined from 12L14 steel apart from the body that is 6061 aluminum

Operating principle roughly to scale. The effective area of the piston is just 0.157 square centimeters or 0.024 square inches, but at 3000 psi that's a force of 72 lbs on the ball locks, in hindsight that difference in diameter could have been smaller.


Cartridge inserted in the launcher

Video with a more detailed explanation of the mechanism and some action shots


Test slugs made from 12 g CO2 capsules, the top two have small screws inserted in the nose and lead filling on the inside.

From top to bottom here are the weights and measured velocities and muzzle energy:

19.8g - 277 fps - 52 ft lbs

13.0g - 401 fps - 72 ft lbs

7.9g - 486 fps - 64 ft lbs

Normally more projectile weight gives more energy, but a dynamic at play here is that the projectile tail being hollow means there is more "dead" volume in the barrel, giving the air more space to expand and therefore dropping pressure.


Aluminum dart with a steel core, weight is 20.7 grams but I didn't measure the velocity, presumably it's below 300 fps.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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mobile chernobyl
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Wed Jan 18, 2023 3:12 pm

This is amazing. I love all the effort to keep it looking stock and completely reversable if desiring to use a conventional flare. The use of the CO2 powerlet sections as ammo is also very clever in a world of expensive ammo. I've utilized them in the past on builds and it was fun shooting full ones into hard targets.

I log back into this site every month to see what's new. This really has me wanting to get a lathe again!

Great work as always!
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Tue Jan 24, 2023 2:35 am

Really nice work, I initially thought I was looking at an actual pneumatic flare gun by its original design, and thought that is cool.

I really shouldn't have considering it was made by you haha.

I love the conversion idea, and effort in keeping it looking stock. Nice valve design too, I cant say I have seen one working like that before.
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