Rules for fighting in confined spaces (tunnels, narrow hallways, spaceship corridors, etc.)
No melee weapons except hand weapons and spears/pikes may be used (and spears only in a straight advance--can't turn corners and attack).
All ranged weapons rifle size or larger have a -1 to hit mod when turning corners (extra time to bring weapon up and fire).
Carbine: use 3, range 8", dmag 1d6+1
Does not incur the penalty for going around corners like a rifle.
CP cost: probably 4, since it's between a rifle and a pistol.
This should be in the Rulebook somewhere:
"Any problem on earth can be solved with the careful application of high explosives"
-Valkyrie (the movie)