Gear Rifles - design assistance requested

[thrash]

Originally Posted by Varyon

Again, the idea isn't to have a mechanical coilgun, just a gun that uses mechanical energy instead of chemical. One of my other ideas was to have a piston... that would engage gears much as you're envisioning the projectile doing, with the piston pushing the projectile forward.

Sounds as if you could be describing a scaled-up Red Ryder BB gun (HT, pp. 88-89). Skip the gears; use air as a working fluid. Put the piston under the barrel and back it with a strong coiled spring. Since you don't have to emulate a lever-action, you can increase the strength of the spring -- say, brace the butt on the ground and use two hands to cock it.

Not as delightfully clock-punk as a gear rifle, but certainly plausible. Real-world metallurgy and gun-smithing weren't up to the strengths and tolerances required, but you don't seem concerned about that.