The primer has some energy, not much but not insignificant. A hot primer and no propellant can be used with a glue-stick bullet for at-home target shooting. (Use a piece of glue stick as the projectile. Has enough energy to perforate a cardboard, but not much more. There’s a howto somewhere on the internet. No recoil, has to be manually reloaded, but good enough for practice and weapon familiarization.)
…howto found.
http://www.ristertech.com/firearms/indoor.pdf
