 Similarities with the 7.62mm Model C and 5.56mm Model L rifles extend to the interchangeability of certain parts.The heart of the operating system is the bolt assembly, which consists of a bolt head, locking piece and two cylindrical rollers, which upon chambering a round, are displaced outwards by angled surfaces in the forward pressing locking piece and into notches in the barrel extension.The geometry of the walls in the barrel extension and the locking piece ensure that once a shot is fired, the bolt head absorbs the recoil impulse from the ignited cartridge through the base of the empty casing and transmits this rearward pressure onto the rollers forcing them out of their sockets and inward at a mechanical disadvantage.