SpudFiles

this is just a theory that's been floating around in my head for a while. A valve on th end of the barrel is opened and the unrestricted air flow fires the projectile.

Unfortunately flawed.

Not only will it's power be limited (because for a considerable time, there will be pressure on both sides of the projectile, resulting in lower net force) but if the ball valve isn't opened very sharpish and cleanly, the projectile is just going to smash into it.

Ragnarok wrote:if the ball valve isn't opened very sharpish and cleanly, the projectile is just going to smash into it.

...et voila, from semi-valveless to fully valveless yay!

could a spring loaded ball valve fix this?

edit- &/or a longer barrel (& proprtionately larger chamber)

It will be worse than if you put the ball valve between the barrel in the chamber, unfortunately the concept is fundamentally flawed.

How is this different then having the ball valve before the barrel?

because you start out with pressure on both sides of the projectile. I just cant imagine it not slowing the ammo down a bit.

Already suggested this idea, ya gotta remember that Ball Valves have a smaller inner diameter as well. The idea works, it's just not useful.

plus, I would imagine it would be nearly impossible to pressureize it with out the projectile traveling at least half of the barrel length, due to the slight pressure buildup behind it...

This should be possible in some way. But then instead I would use a burst disk, which could also be placed behind the projectile but then it wont be a semi-valveless again.