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?
            
			
									
						air comressed spring piston
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!
            
			
									
						And here: http://www.boltsniper.com/BS-9/BS9.htm#design
Enjoy!
Forever dreaming...
						- boilingleadbath
 - Staff Sergeant 2

 - Posts: 1635
 - Joined: Sat Mar 12, 2005 10:35 pm
 - Location: Pennsylvania, USA
 
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)=|====:===========
            
			
									
						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)=|====:===========



