Fresnel
The Antique Shop ended with a SCAR, and the Nano-C from forever ago had a very AR-15 gun as well.

Well the antique shop rifle could just as easily be an acr since both the scar and acr are cosmetically and mechanically similar.
On another note I really dislike the acr since its nothing more than a scar that has the interchangeability of an AR. Whoop de ******** do. b*****d rifle doesn't even have a full-size cartridge model like the scar.
Seriously...why not just pick up an AK instead of going through all the trouble to lug around barrels and other parts and breaking down a functioning rifle exposing it to dirt and sand with a chance of fooling it just to use the same ammo the enemy is using?
The scar might be an unoriginal design since it nothing more than a rejuvenation of the aging fal rifle. Still m4 accuracy and placing second in an extreme dust test speaks for itself where the m4 placed last.