Quote Originally Posted by DrafterAnon View Post
The receiver pictured is actually an AR-10B receiver that was 3D printed by a member of FOSSCAD. It is made to fire the .308 Winchester (7.62x51 NATO) family of rounds, as opposed to the .223 Remington (5.56x45 NATO) family of intermediary rounds.
True. But missing info. The printed receiver is indeed an AR-10 which is designed to run the 7.62 NATO round. BUT, it was NOT modified to do so. The AR-10 was developed by Armalite back in the 1950's specifically for the 7.62/308 round. This is not a NEW design, simply a print of a very very old one.

AR-15s were designed for 5.56/223. AR-10s were designed for 7.62/308. Neither of which have squat to do with 3D printed anything.

Also, the caliber specification is not in the lower, its in the upper. I have one with an interchangable barrel allowing me to fire 5.56/223 or 300AAC/300Blackout while still utilizing the same lower, bolt and magazines. So with a quick swap, I can go from a 22 caliber round to a 30 caliber round.