A brief synopsis
The M 16 was the c601 which was the automatic Armalite 15 rifle was a rifle specifically designed for the battlefield and fires full automatic when designed.
The Sporter/Commanche is an independent design that was specifically designed for civilians and law enforcement. The only real similarities are external and visual only with the exception of the flash suppressor. Internally it was designed for semi automatic AND designed as to not have the ability to just drop in M 16 parts and make it full automatic.
Game. Set. Match.
@Blackvegetable