roygaddis wrote:Not that anyone asked,but in my humble opinion the best expansion chamber is made from a large,(say 20 lb) fire extinguisher tank.The best barrel is made from a piece of 1" copper pipe about 4' long.The best propellant is oxygen and butane,and the best projectile is the bottom end of a ski pole wrapped with cord and topped with shrink tube.You won't blow it up,the smaller barrel concentrates more force,the propellant burns completely and the projectile will penetrate just about anything.Even rock.I've fired through both car doors and into a 55 gallon drum on half a balloonful of oxygen and two tiny shots of butane.C batteries work pretty good,too.Or you can use a 11/4" barrel and use those cheap,driving range golf balls -with the shell taken off- as projectilesThey will bounce back after going through a cinderblock and two bricks,though,so shoot from behind protective cover.
I highly disagree I belive the best chamber construction matieral is any metal rated to high pressure.
And the best propellent is helium.
And the best ammo is anything very heavy.
And the best barrel is a golf ball barrel