SpudFiles

Spring piston mechanisms are all over airguns and perform amazingly well, often producing enough force to even hunt with.

I've never seen a spring piston for a caliber larger than .32 though, and I've been interested in making one in .68 for paintballs.
What calculations do I need to do to figure out the chamber volume and spring strength?
Can I use ggdt in any way to help?

Cthulhu wrote:I've never seen a spring piston for a caliber larger than .32 though, and I've been interested in making one in .68 for paintballs

Here's something: http://airowgun.com/paintball.html

Generally springers are not recommended for homebuilt projects, they require the sort of mechanical force akin to a crossbow when an equivalent pneumatic only needs to be as strong as a soda bottle, if you catch my drift.

If you ran some hand calculations....

Start with a volume of air. Adiabatically compress it to some reasonable value... Maybe 250 psi. Use that new volume of air and the temperature of it. Feed that into GGDT. Once you have numbers you like, back out the spring requirements and you should be in the right ballpark.