USM1 Carbine Field Stripping in GunsWorld

1. First step in disassembly is to fully retract bolt to cock carbine, check to make sure that chamber and magazine are unloaded, and allow bolt to close. Then grasp magazine with right hand, depress magazine catch with right thumb. and remove magazine
2. Unsnap and remove sling from front sling swivel. For field stripping, is not necessary to remove sling from the oiler, which serves as rear sling swivel. However, if complete removal is desired, remove lower loop from adjusting buckle, and withdraw free end of sling from around oiler. Then remove oiler.
3. Using a screwdriver or cartridge rim, loosen front band screw about 1/8" use screwdriver to depress front band locking spring (arrow), and slide front band forward. If front band sticks, place rear of bayonet lug over edge of a table, depress locking spring, pull downward on carbine, and band will slide forward.
4. Lift handguard off barrel and, while holding stock at pistol grip, raise barrel about 15 deg until receiver is released from recoil plate (arrow). Then separate barrel and receiver from the stock.
5. Draw operating-slide spring guide slightly to rear until it is disengaged from operating slide, and then pull to right and forward and withdraw gnide and spring from well in receiver. In some receivers where operating-slide spring fnnctions in a housing in right side of receiver, retract guide and spring, swing lhe housing out and down away from receiver, and withdraw forward.
6. Remove trigger housing retaining pin (if pin sticks, use operating spring guide as a punch). Slide trigger housing group forward off receiver.
7. Pull operating slide slowly to rear until forward face of operating slide stop (a) is in line with rear face of bolt opening in top of receiver. This places guide lug {b) on operating slide handle in line with notch in guideway. Pull slide handle up and to right until guide lug is free of retaining groove.
8. Move operating slide slightly forward to align left guide lug on heavy forward part of operating slide opposite relief cut (arrow) in retaining guideway on barrel. Then rotate operating slide counterclockwise to free guide lugs from retaining guideway, and remove operating slide from barrel.
9. Grasp operating lug of bolt and draw bolt to rear until its face is just back of receiver locking shoulders. Rotate bolt counterclockwise to disengage it from left guideway in receiver. Then rotate bolt clockwise, and tilt it up and right to remove from receiver. This is the last step in field stripping.
10. While holding hammer, pull trigger and ease hammer forward. Insert operating-slide spring guide in hole of hammer spring plunger, pull plunger to rear until clear of seat in hammer move plunger and spring to right to clear hammer. Slowly allow spring to expand, and remove hammer spring and plunger.
11. Drift out hammer pin and remove hammer. Then press on top of sear with thumb as shown and drift out trigger pin. Remove sear and sear spring In replacing sear, free end of sear spring must be seated in rear face of shoulder on bottom of sear. Press sear rearward with screwdriver or similar tool to align trigger pin holes, and seat trigger pin. Newer-type sear has a small hole in upper rear portion, and end of operating slide spring guide can be engaged in this hole and used to assist in pulling sear rearward.
12. Rotate upper rear of trigger upward and forward, and remove trigger through top of trigger housing. In doing this, the trigger spring is unseated from hole in lower rear of trigger housing. To replace trigger and spring, position spring so that loop end rests in slot in upper rear of trigger. Prongs of spring point upward and bear upon upper edge of hole in trigger housing. With right forefinger over top of trigger and spring to hold them in position, press down and to rear as shown. When coils of spring are seated in hole in trigger housing, pull back on fingerpiece of trigger. Do not pull back on trigger until coils of trigger spring are seated or the spring will fly out.
13. With left thumb over thumbpiece of magazine catch, insert operating-slide spring guide or similar tool into hole in lower face of trigger housing, engage tool forward of shoulder on magazine catch retainer plunger, and pull plunger to rear. Remove magazine catch and magazine catch plunger assembly, and then remove magazine catch retainer plunger assembly and safety.