The MkG is our receiver set designed to take large frame Glock-pattern magazines. With so many 9mm ARs on the market, our initiation into a Glock-style magazine fed AR took us straight to .45acp.
The higher pressure generated by .45acp led us to design the Radial Delayed Blowback™ operating system, reducing BCG weight and generating less felt recoil. Since its inception, Radial Delayed Blowback has been adapted to provide the same benefits to other pistol calibers in our lineup.
The MkG is offered in .45acp (but also safely handles 450 SMC)
Virtual Patent Information can be found here.