Originally Posted by Joel
I'm confused as to the actual differences, all the internet sources contradict each other, so I'm checking if anyone actually owns one or at least has some experience with both firearms.
Is it that the firing mechanism and barrel can be interchanged with that of the M16A4 MWS / M4A1 Carbine?
M16 refers to the military designation of the Armalite Rifle model 15. All M16 rifles, i.e. A1 through A4 are capable of semi-auto and either full auto or 3 round burst fire. The lower receiver, bolt and trigger group for a true M16 are different from and therefore not interchangeable with a civilian AR15. In fact it is a federal crime to even possess those parts without a special firearms license.
An M4 is the short barreled, carbine version of the M16.
In civilian firearms the AR15 and M4 designation mirror the rifle versus carbine configuration although neither strictly adhere to the Mil Spec definition of either platform. All civilian AR15/M4 rifles accept the same basic parts differing only in the barrel length and gas port placement and their effect on useable hand guards, gas tubes, sights, etc.