M2A1 .50 Caliber Machine Gun Barrel Carrier Handle

Mishap Prevention article by Bradley Loftis, Deputy Director of Expeditionary and Special Warfare Safety, Naval Safety Command

In late 2022, a mishap occurred where a Browning M2A1 .50 caliber machine gun barrel carrier handle assembly was ejected into the path of the M2A1’s bullets. A bullet struck the handle assembly causing minor shrapnel injury to another M2A1 operator.

M2A1 barrel carrier handle assembly with bullet damage through the cylinder and handle.

(U.S. Navy photo by Gunner’s Mate 2nd Class Kenneth Rettig)

The screw holding the catch securing the barrel carrier handle assembly in place had worked its way loose during normal firing operations. This action allowed the carrier handle assembly to slide rapidly down and off the barrel into the path of the bullets.

Naval Surface Warfare Center Crane (NSWC Crane) Division was notified of this incident and released an advisory message (061744Z MAR 23) to the fleet.

The advisory stated the manufacturer insufficiently staked the carrier catch screw, allowing the handle assembly to loosen under normal operating conditions and eject from the end of the barrel. The advisory directed all commands with M2A1 weapon systems built before March 1, 2023, to complete the steps outlined in the MRJXNR-F21-0150 REV. A – MAINTENANCE REQUIREMENT M2A1 BARREL CARRIER HANDLE REPAIR PROCEDURE. This issue does not affect M2A1s built after March 1, 2023.

U.S. Marines with 3d Battalion, 4th Marines fire an M2A1 machine gun during exercise Fuji Viper 23.2 at Combined Arms Training Center, Camp Fuji, Japan, Jan. 22, 2023. Fuji Viper provides U.S. Marines operating in Japan with realistic training opportunities to exercise combined arms and maintain proficiency, lethality, and readiness.

(U.S. Marine Corps photo by Cpl. Diana Jimenez)

In mid-2023, another carrier handle assembly built before March 1, 2023 was ejected from an M2A1 barrel and was subsequently struck by a bullet. Fortunately, there were no injuries in this case.

After reviewing the OPREP message, Naval Safety Command contacted the mishap command and NSWC Crane to determine the underlying issue.

Was this the start of a new mishap trend? Did the mishap command disregard the advisory message? Was NSWC Crane’s advisory message missing something?

The mishap command stated they received the advisory message and conducted the maintenance steps in the MR-JXNR-F21-0150 REV A before the mishap. Crane stated their steps were sufficient to prevent this from occurring.

The mishap command investigated further. Within a few hours, they discovered the armorer who conducted the maintenance was working on several of their M2A1s at the same time. Usually, that would not be a problem. However, in this case one of the steps in the MR-JXNR-F21-0150 REV A required applying three drops of adhesive to the screw before threading.

Carrier catch screw threads coated with adhesive.

(U.S. Navy photo by Gunner’s Mate 2nd Class Kenneth Rettig)

LESSON LEARNED

When working with adhesive, it is best to complete the next step immediately after application, especially when the procedure calls for a specific amount.

NSWC Crane stated they will add a caution to the MR-JXNR-F21-0150, which should help prevent future misunderstandings or misinterpretations.

U.S. Marines with Battalion Landing Team 2/5, 31st Marine Expeditionary Unit, conduct a live-fire exercise aboard the Amphibious Assault Ship USS Tripoli (LHA-7), in the Philippine Sea, Aug. 25, 2022. Marines maintained their proficiency and lethality with M2A1 .50-caliber machine gun weapon systems while underway.

(U.S. Marine Corps photo by Lance Cpl. Christopher Lape)