Solid propellants are used because they have the highest stability and energy density. A 'mini acetylene tank' the size of a cartridge case woul hold LESS POWER than gunpowder.

I'm checking out of this one as well. It was a fun goose chase at first, but now we're chasing ostriches with laser eyes. As a new technology development engineer, I often use this line: creativity, ingenuity, and innovation are never to be confused with bong water fantasies.