Liquid propellant could be useful in varying the amount used per shot. In some large guns (ship guns mainly) you put bags of propellant in the gun and you're li

Liquid propellant could be useful in varying the amount used per shot. In some large guns (ship guns mainly) you put bags of propellant in the gun and you're limited to whole bags. If you need a half bag you have to vary your aim to get the desired target. It sounds very difficult but might be worth it for space savings and for not having explosive ammo laying around. As for making guns stop working in certain places, why wouldn't crime just target those places? My walk home passes malls, a school, government buildings, and two stadiums. Why would I accept a defensive tool that didn't work most of the time? If we make gun ownership too onerous we risk people ignoring the law altogether - after all the risk of being injured is more serious than being caught defending yourself - which would increase the black market and aid criminals.