Originally Posted by Call_me_Tom
Um, it's a rifle...BCM A4 = 20" barrel. Ever heard of a DMR?
I know, I know, there are many schools of thought on this. Some folks call short gas system's carbines, and full length gas system's (AKA rifle length) rifles.
Then there are the old school folks who call all AR's carbines in reference to the M1A being the only thing that should be called a rifle because it's .30 caliber.
Myself, I feel they are interchangeable and gas system length really doesn't matter.
But, yeah, 16" M4 = Carbine. 20" AR = Rifle. In most circles anyway