+3 BRT M4A1 Bolt Assembly Kit C158 HPT/MPI BAK-M4A1 $95.00 In stock Quantity: 1 Add to Bag Product Details Replacement Bolt Assembly for the AR Family of Weapons (AR15, M16, M4) Carpenter 158 bolt is Shot Peened, HP tested and MP inspected. Bolt is marked "MP". Includes cam pin, CHROME Firing pin and Firing Pin Retaining Pin. 100% made in USA to current USGI M4A1 specifications. Save this product for later Favorite