A trunnion nose guard is a flanged cylinder having internal threads which allow it to thread onto the outer threads of the trunnion nose of a Browning .50 caliber machine gun. The flange of the trunnion nose guard has a face adapted to fit against the front face of the trunnion or against a shim that is interposed between the trunnion front face and the flange. The flange also has at least one hole for receiving a spring-biased locking pin that may be provided on the trunnion front face. The axial length of the trunnion nose guard is selected so that, in use, the trunnion nose guard protects all of the threads of the trunnion nose, but does not extend substantially beyond the end of the trunnion nose.