(_c_) Engage piston tang in the under slot of breech block. (Rear face of tang should abut against the rear wall of slot, and under tang of firing pin should engage in corresponding groove in piston tang.) (_d_) Turn fermeture nut to the open position by passing first finger of left hand in ejection slot of receiver. (When in the open position the ejection slot in the fermeture nut coincides with the ejection slot in the receiver.) (_e_) With the right hand grasp rear of piston assembled with breech block, placing thumb on head of firing pin so as to hold it turned to left behind shoulder of breech block. (_f_) Insert piston assembled with breech block in rear of receiver and push it forward with right hand until it comes to a stop. (Its rear face will now be about 1½ inch in front of rear of receiver.) N.B.—It is imperative that the head of firing pin be turned completely to the left, and that fermeture nut be at the open position. The mechanism should slip into place easily, forcing being neither necessary nor permissible. (_g_) While pressing on the lower end of feed piece with the right hand so as to bring it to its highest position, push forward piston with left hand until breech is closed. 4th.—Insert recoil spring in piston and push forward, allowing a few inches to project to rear of receiver. 5th.—Mount guard. (_a_) Grasp pistol grip with right hand as for firing, making sure that firing gear is properly mounted by pulling trigger several times. (_b_) Engage projecting end of recoil spring in its seat in the guard. (_c_) Bring the guard to a position under receiver so that the two lugs on its head are opposite their mortises in rear of receiver, the trunnions at the front being below and slightly in advance of their sockets in the bottom of receiver. In order that the end of recoil spring remains engaged in its seat in the guard it may be held in place by means of the end of the cocking handle shank. (_d_) Engage lugs in their mortises and trunnions in their sockets by raising guard vertically. (_e_) Draw guard to rear until solidly seated in receiver. (_f_) Screw up locking screw. 6th.—Mount cocking handle. (_a_) Insert shank of cocking handle in opening in guard, the knob inclined at 45 degrees to right, and push forward to a stop. (_b_) Throw knob to left to a stop. (_c_) Push cocking handle forward until home, and then throw knob to right and down as far as it will go. In order to replace a defective extractor or firing pin proceed as follows:— 1st.— Close breech. 2nd.— Remove cocking handle.