My spud gun plans.. pls give feedback on it

[zephir]

I made an eariler topic about building a spud gun, it wasn't about 30 minutes ago i decided to lay it all out on paper.
The goal is to build a gas-operated semi-automatic spud gun/rifle.

The picture is really big, (2217x1700) to show the various tiny details. Its not that big of a problem for people with 1280x1024, but if you have a smaller screen, download it and open with Windows Picture and Fax Viewer. That way every thing is scaled down right to fit on the screen.



As for the fuel, I don't intend on venting the combustion chamber between shots- note that it says O2, not compressed air. So the fuel will be as combustable as possible when it enters tha combustion chamber

The bolt is not drawn in great detail, becasue I haven't really designed that yet. All I know is that it looks alot like a scaled-up SKS bolt.

[jackssmirkingrevenge]

if you can meter the gasses accurately it should work, however I really doubt you'd generate enough pressure in the barrel to cycle a gas mechanism - it's a better idea to try and emulate a direct blowback system as used in submachineguns and small automatic pistols.

[Ragnarok]

Gas operated loaders are not a very good choice for spudguns. I also feel I need to mention that Propane/O₂ mixes are very dangerous things.

It's a nice concept drawing, but I don't think you know how hard it will be to make. I've had a full automatic combustion concept around for a while, but I simply don't have the confidence or skill to build it - and I think that people would vouch that I'm a pretty good builder.
I have got another idea round though, I don't intend to disappoint with my next build.

It's going to be very hard to build, and potentially rather unreliable to boot, because even in the real world of machined and forged rifle parts you get problems.

The SA80 rifle uses this loading principle, and was built professionally - and it's rather notorious for being unreliable.
But equally, the AK47 uses this principle, and it's famed for being so reliable you could practically shove dead rats in through the ejection port and still have it work. (But in fairness, the SA80 is known to be pretty accurate, and the AK47 has "somewhere over there" instead.)

However, unless you're really handy with your building tools, I'm going to have to be pessimistic and say you'll make a loader like the SA80's rather than the AK47's.

[zephir]

the whole reason belind using O2/Prpane was to make it as powerful as possible, the gas system won't work properly if the pressure is too low. It also allows for a small combustion chamber.
I've been building guns for quite some time, not spud guns, the other kind, I see this as a good challenge to make it work.
And I have a nice working (but smaller) rifle to copy from. That one works, and it works very well (except the sticky firing pin issue, but thats something else).

Thanks for your feedback, though.