The C1 Carbine is a modified BR2A2 by Hardpoint. It uses 5.56x45mm NATO rounds. Body shape restructured for lightweight and fast movement Barrel cut down to about 1/2 length New 5.56x45mm NATO mags standardized for infantry using the C1 Carbine Heavy built-in stock replaced with modular buffertube Rechambered to 5.56x45mm The BR1 was originally developed by Jupiter and they shall be credited with most of the design.