Ok I know nothing about guns, except the AA12 and the only reason I know a bit about that is because a friend of mine got me to watch youtube video about it.
The basic idea about the AA12 is that its a recoiless shotgun with fully automatic and normal modes, they've had it put onto drones (basically radio controlled helicopters) and they've fired shots quite happily.
It also can take a variation of sheels, like solid buck, scatter shot, mini RPGs yup thats right when fired out of the gun little stabalizing wings deploy, to be honest even me not a gun fan thinks it sounds a bit nifty
[ame=http://uk.youtube.com/watch?v=p4ebtj1jR7c]YouTube - AA-12. World's deadliest shotgun![/ame]
not sure if thats the correct clip the dam youtube vids won't work at the mo