I like how GURPS treated gyrojets. They were slugthrowers firing explosive rounds, except without appreciable recoil (unless fired on full auto) and with IMPACT (as opposed to explosive) damage based on how far the round had accelerated. Also, the warheads had a minimum arming distance on (IIRC) of about 12 feet (4 meters), so that you didn't take frag damage from your own round.

All of which meant that when it came to fighting inside a starship, shooting someone with a gyrojet was roughly equivalent to punching them with your fist, except you could do it from across the room.