- When they converted the cal .30 U.S. (.30-06) M1919A4 Browning Machine Guns (BMG) to 7.62mm C1 GPMG in the late sixties, they didn't get it right. That was a real pain. Ten years later they fixed some of the problems and re-named it the C5. Once you knew the gun, it was good to go. The key was to pull the trigger bar from the lock frame, insert it into a hole in the barrel casing and then lean on it, bending the tip to the right angle to change the timing of the gun. Purred like a 600 RPM BMG after that, it did.