is the barrel length. The barrel will either protrude ahead of you when you enter a room through a doorway or it won't be in a ready position to hit the desired target. This applies to a rifle as well. A handgun allows you to enter another room without advance notice and ready to fire at what you are looking at. Now if you had a sawed-off shotgun (which is illegal) . . .
Magna est veritas, et prevalebit. Truth is most powerful, and will ultimately prevail.