Gunner, there's some interesting info here on the Lewis & Clark air
rifle, including extensive diagrams of the mechanisms in various states
of safe, cocked, firing, etc. Seems to me a reasonably talented
machinist can build something similar w/o too much difficulty.

http://www.beemans.net/lewis%20assault%20rifle.htm

-Frank



Wow! that is a great page of info!
You can bet I'll be studying that for my next gun.