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

[jackssmirkingrevenge]

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.

[mobile chernobyl]

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!

[ToasT]

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.

[jackssmirkingrevenge]

Thank you gents!

I love all the effort to keep it looking stock and completely reversable if desiring to use a conventional flare.

It also means that the cartridge can be used in any 26.5mm flare gun, I'm really tempted to make a 12 gauge version.

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

The house would feel empty without one

I cant say I have seen one working like that before

The basic principle is the same as used in 40mm grenades for airsoft:

[SubsonicSpud]

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.

Mate, that’s cool stuff, I miss the days of air gun fabrication 10-15years ago. Its awesome to see you got more equipment to work with now, working with epoxy would have been tedious.
Any other stand out builds or ideas on here over the last 10years I’ve been absent?
My holy grail would still be a large caliber cartridge ejecting semi auto. I should complete that QEV repeater build one day.

[mark.f]

Any other stand out builds or ideas on here over the last 10years I’ve been absent?
My holy grail would still be a large caliber cartridge ejecting semi auto. I should complete that QEV repeater build one day.

There's been a lot of small and intricate hybrid builds especially by hectmarr. But ten years? I remember back in 2013 we were seeing some neat piston hybrids or maybe that was a little earlier.
You should get on that QEV repeater, what once cost $200 from places like McMaster or fastenal you can pick up for $20 on Amazon these days.

[jackssmirkingrevenge]

Mate, that’s cool stuff, I miss the days of air gun fabrication 10-15years ago.

The online landscape has changed, social media has effectively killed off this kind of forum for many such hobbies, and the majority of the cadre that was keeping Spudfiles alive has grown up or moved on and there haven't been new generations to fill that gap. It's unfortunate but that's progress I suppose

Any other stand out builds or ideas on here over the last 10years I’ve been absent?

As mark.f mentioned the outstanding projects recently have been by one distinguished Argentinian gentleman, it's a shame that there isn't the same audience out there to appreciate it.

These days I personally seem to do more "restomodding" of air guns like this or this but I have dabbled a little with hybrids recently, more to come soon

[SubsonicSpud]

Mate, that’s cool stuff, I miss the days of air gun fabrication 10-15years ago.

The online landscape has changed, social media has effectively killed off this kind of forum for many such hobbies, and the majority of the cadre that was keeping Spudfiles alive has grown up or moved on and there haven't been new generations to fill that gap. It's unfortunate but that's progress I suppose

Any other stand out builds or ideas on here over the last 10years I’ve been absent?

As mark.f mentioned the outstanding projects recently have been by one distinguished Argentinian gentleman, it's a shame that there isn't the same audience out there to appreciate it.

These days I personally seem to do more "restomodding" of air guns like this or this but I have dabbled a little with hybrids recently, more to come soon

Those hybrid builds are impressive.

100% right about forums dying, I’ve noticed on many other forums as well. It’s a shame because Facebook groups are not great for archive or search purposes.

Perhaps we need to have a SpudFiles group as well

[jackssmirkingrevenge]

While using a single o-ring as both a seat seal and a check valve for filling functioned as a concept, I noticed that sometimes while purging the air line it would not reseal immediately, resulting in lower pressure in the cartridge and inconsistent performance, so I've modified the design with a separate oversized o-ring in a ported groove. This allows air to leak past it when coming from the line but seals in the groove when like line is purged, and so far it seals well. Here is a diagram comparing the first iteration on top and the modified design at the bottom:

[hectmarr]

While using a single o-ring as both a seat seal and a check valve for filling functioned as a concept, I noticed that sometimes while purging the air line it would not reseal immediately, resulting in lower pressure in the cartridge and inconsistent performance, so I've modified the design with a separate oversized o-ring in a ported groove. This allows air to leak past it when coming from the line but seals in the groove when like line is purged, and so far it seals well. Here is a diagram comparing the first iteration on top and the modified design at the bottom:

I like the solution you used and I take note of it for my existential problems with homemade hybrid weapons! It's pretty simple to do and, from what you say, it works well. Interesting!!

[hectmarr]

This modification idea could be used as an easy-to-manufacture check valve. The important thing is that it seals quickly without any spring.

[jackssmirkingrevenge]

Here are some details of the valve, first with o-ring in place and then slide down to show the groove:





Also interesting to note the about of wear happening the two areas where the locking balls contact, on the firing pin as well as the inner edge of the piston:





It doesn't impede function yet but clearly when working with thousands of psi of pressure a harder steel would be a more durable choice of material.

[hectmarr]

Awesome!! You're right, with steel it will last longer... I never thought that the abuse would be so much, but after seeing aluminum, they are very harsh operating conditions. Nice pictures!!

[Anatine Duo]

I agree with Hectmarr that is a neat way to build a check valve.

[jackssmirkingrevenge]

Shame it's so quite in here. Ah well, the tinkering continues and holes are still being blasted though innocent cans

Here is a second version of the flare gun cartridge with a steel chamber and aluminum piston. Fitted with a 6 inch long 0.75 cal barrel it's pushing empty 12 gram CO2 capsules at just under 300 feet per second. That's not too dramatic but at about 510 grains that works out at 100 ft lbs of muzzle energy!