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.30 Cal. Browning Air-Cooled Machine Gun

By Robert Bruce

“The pattern of machine gun operation in Korea is highly unconventional and contrary to the book, but the ground permits of nothing else. Good fields of fire for the machine gun are rarely met...[this] deprives the weapon of its normal tactical power and persuasion, and throws an extra load on the mortars, the BARs, and the riflemen.” Operations Research Office Report R-13, Oct 1951

John M. Browning’s water-cooled .30 caliber M1917 machine gun was introduced late in WWI and was still going strong during the Korean War more than 30 years later. His air cooled, belt-fed thirties, fielded in the late 1920’s initially for cavalry use, also served in “The Forgotten War.” Built on the same receiver but dispensing with the cumbersome and often impractical water jacket, they were considerably lighter yet still capable of sustained fire. This last characteristic was to prove indispensable against massed formations of Chinese attackers.

BARs vs. BMGs

The remarkable Browning Automatic Rifle, also a late WWI development, is unquestionably one of the most highly praised infantry arms in combat accounts from WWII and the Korean War. Not much bigger than the Garand rifle and weighing only about 20 pounds, this selective fire shoulder weapon was highly portable, accurate, dependable under all weather conditions and hard-hitting. Able to punch out powerful .30-06 bullets at a cyclic rate of some 550 rpm to a maximum effective range in excess of 500 yards, its only significant limitations came from 20 round magazine feed and lack of sustained fire capability.

So, because of the tendency of both North Korean and Communist Chinese to utilize “human wave” assault tactics, vastly outnumbered units of the US Army and Marines counted on belt-fed Brownings of .30 and .50 caliber to even the odds of survival. (A separate feature by Robert Bruce on the .50 cal. M2HB M2 is included in this issue - Editor).

The M1917A1 water cooled .30 cal., capable of almost continuous fire limited only to supplies of ammunition and water, was theoretically ideal for this task and could be found in the weapons mix of every infantry battalion. But, as previously stated, this multi man crewed 95 pound system was found to be impractical due primarily to excessive weight and its need for skilled and frequent attention.

In contrast, the M1919A4, an air-cooled version of this same gun, weighed considerably less at about 50 lbs. on an M2 tripod. Its maximum effective range and cyclic rate of fire were essentially the same as that of the heavier gun with the added benefit of dispensing with water for the jacket (and anti-freeze in winter) plus all the special parts, tools and skills needed to keep the water from seeping out without locking up the barrel. Broken down into three main loads of gun, tripod and a good supply of ammunition, the A4 system was far more easily humped up and down the jagged ridges that characterized much of the Korean countryside. Problem solved, right?

“The interrogations indicate that in the mind of the average gunner “firing in short bursts” is about synonymous with lifting the finger from the trigger for a few seconds at frequent intervals rather than resting the gun at all times when there are no manifest targets and no compelling tactical reasons for firing. This affords no relief to the weapon as far as over-heating is concerned, and it does not conserve ammunition.” ORO-R-13

There is no free lunch, however, and the A4 Browning had its own limitations. In addition to the need for frequent cleaning and proper lubrication that varied depending on weather conditions, the air cooled gun would overheat rather quickly from prolonged firing. Despite having a heavier barrel that acted as a heat sink and radiator, only about 1 belt - 250 rounds — could be fired in a minute before a too-long pause for cool down or panic barrel change was necessary. Since swapping barrels was a several minute exercise that also required careful setting of headspace, this was often a life-threatening problem.

Combat Crapout

“Not less surprising is the percentage of failure in machine gun fire at some time during the course of the average engagement because of mechanical trouble of one kind or another, faulty handling by the crew, etc.” ORO-R-13

Interviews with Eighth Army troops following combat action in the winter of 1950-51 suggested a failure rate for air-cooled thirties in excess of twenty percent. Various reasons were both observed and theorized, including poor mechanical training, neglect of regular and proper cleaning of the guns, and failure to keep ammo clean and correctly seated in the cloth or metallic belts. None of these, by the way, is inherent in Browning’s excellent design that - in the proper hands - is highly regarded for combat efficiency.

The ORO report cites an average figure for company-sized infantry units of just two guns in operation per engagement and, all too frequently, not even one gun was working. When these luckless GIs experienced a total loss of their base of fire belt feds in the heat of an assault or defense, the full burden of firepower was thrown primarily on BARs and M1s. Fortunately, both the auto rifles and the Garands were almost invariably up and running no matter how hostile the weather or their handling.


Disappointment with combat utility of the A4 and A6 Brownings in Korea led to postwar development of the M60 General Purpose Machine Gun. Fielding of the new “Sixty” and its companion, the selective fire M14, was nearly complete when America began sending combat units to yet another Asian misadventure. This time it was Vietnam.

Primary References

FM23-55 and TM 9-2005

Brig. Gen. S.L.A. Marshall, “Commentary on Infantry Operations and Weapons Usage in Korea; Winter of 1950-51,” Johns Hopkins University, Operations Research Office Report ORO-R-13, Oct 27, 1951


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