SpudFiles

I just had an idea:
A spring piston design where the spring provides the energy (like a break barrel airgun). The difference bing that my design has compressed air behind the piston so it wouldn't need a really strong spring. Although it would need a strong trigger design.
I was making a diagram but messed up and got pissed off so yeah... any thoughts?

It may work... however, the simple piston design would work even better (due to less force pushing the piston against the sealing face) and is simpler to make.

Ok, I know these are nerf but you can learn a little from the design. These are just the type of pistols you are talking about. Looky here: http://www.boltsniper.com/Homemades/BSarmory.htm
And here: http://www.boltsniper.com/BS-9/BS9.htm#design

Enjoy!

I would either skip the springs entirely (and just use compressed air) or skip the compressed air entierly and just use a spring.

I have an interesting idea for the air-only meathod:
Have a valve (any valve) connect a large chamber to a small chamber. When oppened, the small chamber fills untill it overwelms a burstdisk, and that air accelerates a piston down the pump tube (until it hits a stop).

(chamber)=/=(small chamber)=|====:===========