Bushmaster marks the chrome lined barrels with B MP 5.56 NATO 1/9 or 1/7 and HBAR if it is a heavy barrel. The 6 position telestocks have the Bushmaster snake logo. Upper receivers may have a "L", "O", "Y" or inverted "T" stamped onto the rear of the upper receiver takedown lug but some are not marked. The inside of the upper receivers is a lighter gray color than the outside as a Mil Spec dry film lube is baked onto the inside which many other manufacturers do not include. Bushmaster uses an allen head cap screw that uses a 3/16" allen wrench for the pistol grip screw. Steel parts are manganese phosphate finished and aluminum parts are hard coat anodized. The barrels have forged front sight bases installed with taper pins and not castings. Polymer handguards have heat shields installed.