My Idea : a Battle-bot that shoots Golf Balls

[benstern]

That short of a barrel and with such a small chamber that golfball won't have much energy. Even at your 75-100 psi and with a piston valve it won't be very powerful. Not powerful enough to punch through any sort of significant armor. What valve dare you planning on using?

[benstern]

I would go for a piston valved pneumatic ram with some sort of stabbing implement that won't get stuck in another robot.