In the event the cam roller slides ahead, it pushes the feed cam to the right versus a return spring. If the cam roller slides backward, the spring pushes the cam back into the remaining. The feed cam lever is hooked up into a spring-loaded pawl, a curved gripper that https://machguns.com/product/lot-1496-rock-island-armory-m60-machine-gun-class-iii-nfa/