Simple coaxial shotgun

[Marffy]

So i finally finished my muzzle loading piston air gun. I've only taken it to 150psi but its got some good power, can't wait to bump up the pressure.

Specs:
Chamber: 2' .75" galvanized steel
Barrel: 36" .5" OD steel tube ~.44 cal
pilot: 1/4" modified blowgun
fill valve: schrader


the piston is a wine cork, with glue on one end, and a bolt thru the whole thing that attaches a neoprene washer as a sealing face. I'll get images up next time i open the gun up.





Overly complicated barrel support:










overall i'm very pleased with how it turned out, i still have to sand the stock some more and rig some iron sights.

I'm also going to test it for leaks underwater but for now it seems to hold air just fine.

[Lockednloaded]

Nice simple gun you've got there, great work with the stock.

Did you roughen up the inside of that hose barb and your barrel? If so it looks like you're ready for some high pressure fun

[Marffy]

Nice simple gun you've got there, great work with the stock.

Did you roughen up the inside of that hose barb and your barrel? If so it looks like you're ready for some high pressure fun

no, i just left it as i got it. i didn't think of doing so untill after i glued it. one side is filled with hot glue so i think the piece will hold together but it just might leak at high pressure.

[jackssmirkingrevenge]

Looking good, hope your piston can take the strain of higher pressures.

[jrrdw]

Looking good, hope your piston can take the strain of higher pressures.

I was also wondering about that. Cork piston could be a first here...

[Marffy]

Looking good, hope your piston can take the strain of higher pressures.

I was also wondering about that. Cork piston could be a first here...

I used to shoot corks out of 3/4" barrels so thats where i got the idea. Its working great so far. It doesn't need a bumper and won't crack in half

[jackssmirkingrevenge]

Do you mean a cork cork or a rubber "cork"?

[Marffy]

Do you mean a cork cork or a rubber "cork"?

wine cork, so.. rubber cork.

[Zeus]

We've been using them for ages, we assumed you meant a cork made from cork.

Down here, I've never seen a rubber wine cork.

[Marffy]

heres a little update:

barrel in the chamber:


the piston:


it started to leak today so i opened it up to see what was wrong

[drmoreau]

I'm curious about the firing mechanism. I get how you've got the schrader valve to put pressure into the system, but it looks like your trigger is an air blower attachment for an air compressor system....when you pull the trigger won't all of the air just come out of it where the trigger is though? How is this supposed to release the pressure down the barrel? I'm confused.

[jackssmirkingrevenge]

I'm confused.

No you're not: http://www.spudfiles.com/forums/piston- ... t8157.html

[drmoreau]

honestly the diagram in the link seems incredibly complicated for something as simple as releasing pressurized air, lol.

even then, I still don't see a pressure tank on this gun so I don't see where the air is coming from to fire the projectile when the valve is released.

[jackssmirkingrevenge]

This is basically how it works:



In the case of the subject of this thread, instead of filling and firing with the same tyre valve, he's using the tyre valve for filling and the blowgun valve for firing - but the concept is identical.

[drmoreau]

neat, but I don't like lots of parts, especially moving ones, lol. i'm a firm believer in KISS (keep it simple stupid), hehe.

thanks for explaining it though.