Really nice gun, I'm assuming you screw on to the Schrader valve instead of using a check valve? Also, do you screw the barrel assembly onto the breech each shot or does it slide in? Thanks, beautiful work !

Thanks Kilash! I used a muzzle energy calculator on a different site entering just muzzle velocity and projectile weight and I think it came up with 115ft/lbs so your calculation is probably right on the money. It has a piston valve which is almost air tight while being very low friction, currently ...

Its .55 inch ID, ty

Barrel is 42 inches.

Thanks! I kind of assumed there was something else going on that I wasn't accounting for. Math has never been my strong suit, but at your leisure could you tell me what energy performance you would anticipate from my launcher?

Chamber Vol. is 18.7 cubic inches
Barrel Vol. is 6.7 cubic inches ...

You probably want something like this: http://www.spudfiles.com/forums/simple-cannon-t24849.html

QEVs are dirt cheap online: http://www.spudfiles.com/forums/semi-auto-valve-for-under-20-t23626.html

Since NERF darts need so little air per shot, you could probably realistically make a semi auto ...

Well, honestly I wasn't sure. I was thinking about a spring which could act as a piston sealing aide and also as a bumper, which I guess at 2-500 psi doesn't have to be extremely stiff, I'm just trying to find a happy medium between reliable valve sealing and not closing prematurely.

I am designing a new launcher based on my experiences with my first piston launcher, and my design necessitates a chamber-side fill port with a multishot capacity, ideally 3 200+psi shots. I'm just wondering if anyone who has developed a piston with a return spring has noticed any notable ...

I suppose a ballistic pendulum would simply mirror the muzzle energy calculator?

Thanks, I bookmarked that thread. From what I took from it was, Faster, Harder, Longer....hehe Debbie Does Dallas could teach shooters quite a bit about target damage. Seriously though, I suppose the best judge of terminal performance is depth and diameter of penetration into a uniform substance.?

Hey guys, I searched for an answer to this query, but didn't find any definitive answer. So I use a muzzle energy calculator for my launcher, which for specificity is a standard piston pneumatic, muzzle velocity is approximately 580 fps with an approximately 160grain projectile. Seems easy, plug it ...

Copper has the advantage of being easily soldered to other copper parts, steel on the other hand, can be brazed, but most often thought of as a welding material. I would prefer steel seamless tubing over almost any other material, but it is not readily available where I live like copper, and I haven ...

weapon?! Looks like a modded writing instrument to me

I don't want to get caught up in a bidding war with you Brian 8) ... Jack was the all metal version constructed for a customer? Would you forsee any US Customs issues shipping to the US?

You will have to purchase a pump which suits the intended pressures. For self contained shooting without pumping, you are entering the territory of PCP commercial airguns. These guns typically have a chamber containing enormous pressures, measured in 1000's of psi's.
A trade off could be a chamber ...