Why? Why not? I know this has probably been discussed time and time again but I'm thinking about doing this for my next AR build. Obviously the pistol calibers (9mm will be where I go) don't need the barrel length of a carbine and I'm thinking something like 7-9" would be ideal but still might be too much barrel. Well, maybe not "too much" so much as not needed. Or maybe 5" and a can? What say those of you who actually know what the fuck you're talking about? Primary use would be HD and/or Car rifle. The only valid argument I can think of this comes from a fight stopping ballistics point of view. The reason we don't carry rifles is because they're too big so we carry inferior pistols. Going to a rifle will give stability, higher sustained rate of fire, longer sight radius, increased shootability, etc but the ballistics are the same. Is the con (sub-par ballistics) worth the pros ?