My 80 was missing one of the 0.05mm shim washers fitted to the rear of the recoil sled, I've made one out of a 0.05 mm feeler gauge. It now shoots and the action recoils and stays in the rear position. Im I right in thinking if I push it forward itll move around forward to back, and once cocked it'll move around freely or should it lock in the forward position?