TM 10-3930-669-34 13-2.  MAST ASSEMBLY REPLACEMENT/REPAIR (CONT). (17) Remove two rollers (62) and shims (63) from center rail (58). (18) Remove two screws (64) and lock washers (65) from center rail (58).  Discard lock washers. (19) Remove two screws (66) from end of center rail (58). WARNING Use care when removing or installing snap   and   retaining   ring.      Snap   and retaining rings are under spring tension   and   can   act   as   projectiles when released and could cause severe eye injury, (20) Remove   retaining   ring   (67),   spacer   (68),   and roller (69) from center rail (58). 13-12