I've always wondered about the "carbine" barrels...Using a commercial cartridge, one that won't blow the extractor through the breech block, aren't you reaching the point of diminishing returns with that length barrel??? By the time the bullet reaches the muzzle (I'm theorizing), the pressure has dropped and the friction from the longer barrel with lowering pressure is actually slowing the bullet instead of accelerating it...
That's my line of thinking anyway...
