I don't like the idea of making the carbine semi-auto because that would completely change the kind of gun it is. The carbine currently takes a good bit of skill and pacing to use correctly, and I like that. Nobody asked for a giant pistol.
Keep current carbine's stats, but make it ignore armor.
Slower to kill, but consistently slow to kill (almost always takes two shots) = ???
Keep current carbine's stats, but make it ignore armor.
Slower to kill, but consistently slow to kill (almost always takes two shots) = ???