pneumatic pen gun v2 - added video

[Sticky_Tape]

Out standing proformance there JSR now in the words of the noob mak it hybrid it'll be powerfuller.

[jackssmirkingrevenge]

Coincidentally I happened across a re-run of the Mythbusters "ice bullet" episode where they make a pneumatic umbrella gun. Their effort was pathetically weak, especually considering it was filled with high pressure from a SCUBA tank, as well as being completely obvious.

If you had to stretch this design to the length of an umbrella or a cane and fill it to say 1,000 psi you'd get pretty devastating results.

[inonickname]

People try (like that article on the guy who died from spudgunning(the article writer, not the guy), and the mythbusters) but there just seems to be something missing that isn't understood by the non spudgunning types.

Very nice gun though! A machined version to run on 3k psi (the hi pressure manual pumps) would be destructive.

[jackssmirkingrevenge]

I managed to get a velocity reading for a half gram lead slug, it was plodding along at a respectable 364 feet per second, that's better muzzle energy than most CO₂ pistols

[POLAND_SPUD]

pen guns are not quite what I like but I have to say you are really skilled at making them... they look very well built

you might try to get a fridge compressor for this... considering what pressure maggotman has reached by supplying pressurised air to the air input I suspect that you can safely up the pressure twice

[jackssmirkingrevenge]

I've been on the lookout for a fridge compressor for quite a while now, I'd be comfortable taking it to 1,000 psi. I want to see if I can make a schrader adapter for my SCUBA tank in the meantime.

I also have a CO₂ tyre inflator on the way that should make for a handy machine pistol and I'll be wanting to use HPA in it too.

In the meantime, I'm working on the marker project I had thought up a while ago

[ALIHISGREAT]

In the meantime, I'm working on the marker project I had thought up a while ago

nahhh thats too easy for the pen-gun-king... i challenge you to make a semi auto self contained pen gun (ha i'd like to see that done!)

[inonickname]

In the meantime, I'm working on the marker project I had thought up a while ago

nahhh thats too easy for the pen-gun-king... i challenge you to make a semi auto self contained pen gun (ha i'd like to see that done!)

I just quickly drew this up. He already has a semi auto *small* gun.

The idea of this is it has 2 chambers, a large pressure chamber and a smaller firing chamber. The small firing chamber is repressurised after each shot by the large chamber (using a valve - good luck getting one small enough though. Perhaps a small sprinkler valve?). The magazine would hold few bb's to try keep with a pen/marker shape. After it is refilled it can be capped off. It is gravity fed, with a magnet to hold the bb until firing. The firing valve is basically a piston which blocks the barrel, and when a valve is opened from the larger tank air presses the piston down (which is sprung) allowing the chamber pressure to go through, firing the gun. Releasing the pilot pressure from the main tank closes the valve, allowing the weapon to be re-pressurised. BTW the pressure chamber is over the barrel like a co-ax but is separated.

With a lathe you could probably build it to fit a large-ish marker.
I guess it could be adapted to use a co-ax type setup instead of the piston valve.

Good luck if you try it, and I like the look of the marker gun.

[jackssmirkingrevenge]

Semi auto is impractical on such a small scale (unless you conjure up a tiny hammer valve in order to conserve pressure reserves) however a burst fire pen gun in this vein but firing say 2.5-3mm lead shot is very do-able, hmmm...

[Dgealy]

I am currently building my own pen gun pump. I was sliver soldering a schrader cap to my pump, using the valve stem as the actual check valve.

My question: Can I pump this thing up to say 300 PSI just by over-pressurizing the schrader, or must I modify it in some way?

[jackssmirkingrevenge]

Gipetto found he needed around 70 psi to crack the schrader open if I recall correctly, if your schrader is of the exposed spring variety (have a look here) then you might be able to weaken the spring and get maximum pressure.

[SpudUke5]

I just got some 1/4inch thick rubber from mcmaster, and i cant find a way to cut a nice piston from the rubber so im curious on how you cut such a nice piston shape.

[FishBoy]

I just got some 1/4inch thick rubber from mcmaster, and i cant find a way to cut a nice piston from the rubber so im curious on how you cut such a nice piston shape.

I was wondering the exact same thing... Perhaps heated wire?

[SpudUke5]

Well thats a possibility, that got me thinking. Maybe i can heat the chamber (brass) and then push it through the rubber so that i get a nice piston cut. That might work.

[jook13]

when I made my pengun, I just used a section of the pipe, put the end of the pipe on the rubber and used a hammer to "stamp" out a section. It works great!