old school air rifle

[volta]

i've been building combustion and simple pneumatic launchers for a while now. although, this is the first time i've posted in a spudding forum. i'm also an avid airgunner.theyre both great hobbies in their own aspect. no doubt, but i've had the idea of combining the two for a very long time. let me tell you what i'm picturing.

i basically want to make a .40 to .50 caliber, smoothbore, co-axle piston cannon small enough to be mounted (attractively and effectively!) in an air rifle stock. the chamber would be 3/4 inch thick. the chambers also have to be able to take fairly high pressures. since the volume of the chamber and length of the barrel will both be cut a little shorter than optimal, the high pressures will have to be used to achieve the fast, 450 fps velocity i would love to have.

the reason i am posting this here is because i have a few problems that i've run into during planning. the first is the trigger. i could use a blowgun, but that is very common and i dont think it would make a very good triger for a rifle/shotgun that i plan on being accurate. any ideas are appreciated on that. also i just wanted to know what everyone thought about making the chamber out of 3/4 inch pvc pipe and the barrel out of a .40 blowgun.

if i should have posted this in the "mini" section then i am sorry, having it moved to where it belongs mould be much appreciated.

thanks for listening. any comments or advice is also very much appreciated.

thanks, colt

[jrrdw]

Got any diagrams drawn up? Sounds very interesting. How would a blow gun make it inaccurite?

Welcome to Spudfiles.

[biggsauce]

What pressure do you want to use? That may affect what materials you use for your chamber.

Sounds like a cool idea, do you pln on posting your other cannons?

[Ragnarok]

since the volume of the chamber and length of the barrel will both be cut a little shorter than optimal, the high pressures will have to be used to achieve the fast, 450 fps velocity i would love to have.

450 fps isn't particularly hard to achieve, pneumatic cannons have managed twice that in the past. It is easily possible, but it will depend on projectile weight, and to some extent on your chosen barrel length.

PVC pipe for the chamber will limit your options on pressure to some degree, but rated low diameter pipe is fairly hardy. Even then, it shouldn't be pushed too far - but a member known as JSR (Jackssmirkingrevenge) has pressurized such kinds of pipe to around 400 psi - take that with a pinch of salt, as not all types of pipe are the same.

My personal choice would be something around 1" copper - but then, I build everything from copper, so that's hardly surprising.

I haven't used many blowguns in my time, so I can't be much use, although many people will swear by them. Myself, my favourite trigger so far is a slide/sleeve valve, although they are a little pricey.

Now, you need to discard any ideas you have of these launchers being particularly accurate. If they're made well and use consistent ammunition, they can hit moderately sized targets consistently at fairly short ranges, but they are far from pin-point accurate.
Some of my launchers have shown good results on "accuracy", more than I originally hoped for when I made them, but still far from a rifle (be it a real one, or an air rifle)

By the way, this doesn't need to go in the Mini section. That's mostly reserved for launchers of "pocket-size" or close to that.

[Gippeto]

Ummm, I think this might be of help.?

http://www.spudfiles.com/forums/high-pr ... 12803.html

Edit #1 And this;

http://www.trackofthewolf.com/(S(nzh5rizwbdwwduvvgtsc1x45))/categories/tableList.aspx?catID=14&subID=142&styleID=483

Edit #2 :oops, you did say smooth bore didn't you.

[volta]

ragnarock, i know it will never be truly accurate like any of my airguns. i am merely trying to replacate what the old airguns achieved. and after all, they did have smooth bores and used very simple valves of low pressure as well. specifically i'd be happy being able to shoot an index card at 10 yards. aside from that the real idea was to make a shotgun. i think some small sised shot would wreak kavoc on cans if i can get it up to speed.

to everyone else, thanks. i appreciate the thoughts. i will be posting my cannons here pretty soon if you'd like.

gippeto, i'm definately going to send you a pm. lol that gun you made is very simular to what i want to make.

[keep_it_real]

This is how I set up my trigger (current project). It's actually modded for semi auto but you don't need to do that.