SpudFiles

i want to make a single shot pellet gun, mainly for blowing cans in half, i think im going to make it .22 cal, and i want to know how you think i should make it, what valve, and whatwhat size pipe i can use for .22 cal pellets?

You arn't going to be "blowing [aluminum] cans in half", even if you somehow mannage 1000 fps. My bet is you'll want at least 1500, probably 2000 fps (but there's no testing or math behind this) but that's a bit hard to achieve with compressed air/hybrid/combustion cannons (my only experience is with 1200 and 3700 fps. One doesn't accomplish it, one is WAY overkill).

If you want to damage cans, though, you'll manage quite well with a few hundred fps. Acheiveable with decently high pressures in a pneumatic launcher, I'm sure.

I'd go with .25" spheres in 1/8" sch 40 pipe, which are acctualy .001" too big.

i didnt really mean in half, just blowing holes in it. where would i get 1/8" sch 40? and .25 cal metal balls?

It's possible If you shake them up vigorously for a couple minutes , then shoot them with bb's, pellets, or marbles, they all work, heck my wrist rocket can blow shaken up cans in half

i've been tossing the idea of building a pellet gun around in my head for a while.
my idea was to use a valve from a paintball gun (i dont know the name of the type, but in a few of my pb guns have a valve body which is held closed with a spring, when the heavy bolt slams forward, striking the valve with enough force to open it for a split second, delivering a measured blast of c02 or air)
i think that if i used a heavier spring on the valve (to withstand higher chamber pressure) and if i drastically increased the weight of the bolt which strikes the valve, to open valve further and for slightly longer, i would get the most from the valve.
i would use a rifled pellet barrel with .22 cal pellets fed through an underbarrel tube magazine (i'll borrow one from an old .22 LR rifle)
i'd make a bolt action mechanism to feed pellets and fire it with a HPA paintball cylinder.

i know i have left out alot but its hard to transcribe the picture i have in my head into a coherent typed format

then draw it dinsdale?

I have always toyed with the thought of an unregulated CO₂ or HPA gun, (regulated to at least 1,000 or 800 PSI), with a hammer valve or a really tough coaxial valve enclosed in a milled steel receiver and threaded on the end to accept a Remington .308 match barrel. You'd have to breech load each round, (which I still don't know how I would accomplish), but it would still be pretty neat.

i've been toying with the idea of a miniaturized piston valve for a pellet gun instead of the hammer valve and set it up to use a whole 12 gm co2 cartridge.

for a breach loader you could make a single shot bolt action receiver from a short piece of 1/2" ID heavy walled steel pipe, and a short piece of 7/16 OD pipe; (you could use 3/8 OD as well, but it will be sloppy)

Cut a loading port large enough to feed your ammo, and a slot for the bolt handle to ride in into the piece of 1/2" ID pipe, cut o ring grooves into the smaller pipe, so that it adequately seals the cutout area when the bolt is closed. drill and tap into the wall of the small pipe so that you can thread a long machine screw into it, this is your bolt handle. thread the inside of the small pipe, and attach a short piece of flexible hose to connect to your chamber. insert the bolt into the receiver, attach machine scew (use loctite)
the action should open enough to easily feed a round and close tight with o rings ahead and behind of the cutout. there should be enough slack in the hose that it doesn't impede bolt movement.
attach a barrel to the front, and a power source to the rear, and you have a slick bolt action air rifle, if you use a nice rifled barrel on it and a regulated hpa system...wow