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Ordnance Notes -- by Bob Stoner GMCM(SW) Ret. AN/M3 .50 BMG Air-Cooled (Aircraft) The AN/M3 aircraft gun is an extensively modified AN/M2 gun. The gun is distinguished by a massive pneumatic buffer at the rear of the receiver and a muzzle booster cap at the end of the barrel jacket. The gun was extensively used on late 1940s and early 1950s fighters until supplanted by 20mm machineguns. No sights are furnished on the gun because the sights are considered a part of the airplane. Changes to the AN/M3 gun relative to the AN/M2 are: the bolt assembly, oil buffer body, and barrel extension are modified. The oil buffer is not filled with oil. The breech locking cams are riveted to the inside of the receiver on the AN/M3 instead of being attached to the oil buffer body as in the AN/M2. The bolt switch cam and extractor cam are different. The extractor assemblies are different. The top cover has more massive parts (AN/M3) and is not interchangeable with that of the AN/M2 except as a complete unit. The pneumatic buffer on the AN/M3 is designed to absorb the greater recoil forces attendant to the gun's higher cyclic rate. Cyclic rate of the AN/M3 is 1,050 to 1,150 rounds/minute. The most famous use of the AN/M3 was by the American F-86 Sabres against the Communist MiG-15s during the Korean War. The massive firepower represented by the six .50s on the Sabres more than compensated for the two 23mm and one 37mm cannons of the MiG-15 (whose guns had been designed to shoot-down bombers). The AN/M3 gun we put on our MSSC at SEA FLOAT was recovered by SEAL Team ONE, Detachment Golf. I talked them out of it as a firepower upgrade for the MSSC. I retrofitted a set of spade grips in place of the pneumatic buffer, replaced the AN/M3 buffer with an AN/M2 oil-filled buffer, replaced the M3 bolt assembly with an M2 bolt assembly, and the M3 top cover assembly with an M2 top cover assembly. The cross-bred M2/M3 gun worked, but I was never able to work out its teething problems due to lack of range time. I believe part of this had to do with the timing of the gun (8 to 12 barrel clicks instead of 3 to 5 on the AN/M2HB guns). However, the one time that the gun worked flawlessly was the time we got shot at by an Russian RPG-2 (Chicom B-40). Their rocket lost a fin which caused it to tumble in flight. I saw the launch site and splattered it with the M2/M3 hybrid. One burst ate half of the 426-round ammunition box and it was dead-on. © 2002 Bob Stoner
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