Have a helper hold barrel with a strap wrench while torquing the spanner nut. j. Using spanner wrench, torque spanner nut to 135 ft-lb ± 10 ft-lb (183 N-m ± 14 N-m).

Spanner Nut Threads

ribbed (nitride or chrome) barrel assembly without locking tab washer k. Thread spanner nut (6), flat side first, until it lies loose on 25-mm barrel (7).

l. Position locking tab washer (11) with tabs pointed towards spanner nut. Align locking tab key (12) with barrel keyway (10) and slide locking tab washer until it lies loose on 25-mm barrel (7).

m. Apply antiseize compound to threads of 25-mm barrel (7).

n. Thread muzzle brake (8) completely onto 25-mm barrel (7) until snug.

o. Back off muzzle brake (8) until barrel keyway (10) aligns with muzzle brake keyway. Do not turn muzzle brake more than one complete turn when aligning keyways.

p. Install machine key (9) into keyway (10).

q. Re-position locking tab washer (11) and thread spanner nut (6) on 25-mm barrel (7). Tighten spanner nut (6) against muzzle brake (8), machine key (9) and locking tab washer (11).

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