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.

Epilogue

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

By Robert Bruce

“The introduction of the 3.5 inch bazooka in Korea occurred at a time when the main objective was to stop enemy armor. It proved effective in this use during a critical period. So the troops were won to it, and so being, tended to discount the worth of the 2.36 rocket launcher. Then came the phase when enemy armor was no longer a problem, and the prevailing tactical situation required the frequent destruction of large numbers of enemy personnel at close range as they attacked our hilltop perimeters. The 2.36 would have been a valuable adjunct of the infantry line at this point if used mainly as a man-killer.” Operations Research Office Report R-13, Oct 1951

The highly innovative “Bazooka” proved invaluable in the Korean War against enemy tanks and defensive emplacements. Introduced in a crash program during WWII, it had served exceptionally well as a remarkably effective weapon for infantry fighting in a variety of situations from anti-personnel to anti-tank engagements. When the initial 2.36 inch model proved inadequate against German armor, Army Ordnance essentially copied the bigger rocket from a captured enemy 8.8 cm PANZERSCHRECK (itself an improved version of one of the first American bazookas captured in Tunisia) and the M20 3.5 inch Rocket Launcher was born. What goes around, comes around….

At the end of WWII production of this new “Super Bazooka” was curtailed and, tragically, it was not available in sufficient numbers some five years later when Soviet-supplied T34 tanks first made their appearance in the Korean War. Numerous American units were overrun by these formidable battlewagons that, with the exception of a hit in the tracks or from above, were unstoppable by the little 2.36 in. launcher. The Army began a crash program to send all available 3.5’s to Korea and emergency contracts were signed to manufacture additional launchers and rockets.

“Sitting a little way up the slope from Watchel and the machine gun was Sgt. Paul West, with a 3.5 launcher in his lap…he raised the launcher and let go one rocket. His first round hit the Chinese mortar dead-on – at 225 yards range. It was the luckiest kind of a fluke shot. That cooled off the enemy force attacking up the draw.” ORO-R-13

Targets of Opportunity

Interestingly, combat reports showed that troops who had considered themselves highly fortunate to get the bigger bazooka, rarely used them against enemy infantry. This is puzzling, given that the standard high explosive anti-tank round was more powerful than that of a 60mm mortar, and the spectacularly effective white phosphorous rockets were in plentiful supply. Instead, the most common use of the 3.5 was mainly against machine guns, buildings where enemy skirmishers had taken cover, and occasionally for bunker-busting.

Recoilless Rifles

“…the basic idea of the recoilless rifle, which ranks with the bazooka as one of the most impressive ordnance developments of WWII…put artillery fire power in the hands of the individual foot soldier, for it required no ponderous carriage or recoil mechanism.” The Ordnance Department: Procurement and Supply

Only a hundred or so 57 and 75mm recoilless rifles had reached GIs in Europe in the last several weeks before Germany’s surrender, robbing these extraordinary weapons of honors they most surely would have won. Another bit of American reverse-engineering of an enemy weapon, in this case the 75mm L.G. 40 Recoilless Airborne Gun, it is similar in profile and employment to the bazooka, but operates on a completely different principle.

Instead of serving as merely a tube to point a rocket in the right direction, the recoilless rifle is a highly novel artillery piece that is light enough to make it readily man portable, yet fires powerful conventional projectiles. This bit of physics-defying magic is accomplished by perforating the walls of the cartridge case with large numbers of holes and placing the round in a partially open chamber with venturi tubes that allow escape of carefully calculated amounts of propellant gas.

On firing, sufficient pressure is built up to kick the round downrange at a serviceable velocity, but simultaneously, the rest is vented rearward. Thus, Newton’s Third Law Of Motion is not violated so the weapon does not recoil. The 57mm version can be readily shoulder fired, and the bigger 75mm is handled nicely on an ordinary machine gun tripod. Spin-stabilized by rifling inside the barrel, the projectile is fast and accurate both for direct fire and high angle employment at remarkable range.

No Free Lunch

On the negative side, this rearward venting of gas is extremely energetic and has some nasty side effects. First, there is a highly dangerous backblast area that must be kept clear of friendly troops and disallows firing from a bunker or backing up against a hillside. Also, its noise is painfully deafening and the nighttime firing signature is spectacularly bright. Finally, the weapons and their ammunition are significantly heavier than the bazooka, increasing the burden of the infantry unit struggling up and down the jagged ridges that characterized much of Korea’s terrain.

Balancing the equation, high explosive, anti-tank, and white phosphorous smoke ammunition was made for these unusual weapons, giving them roughly the same capabilities as the bazooka, mortar, and pack howitzer. The efficiency of this system was such that, in the peaceful years following WWII, recoilless rifles were thoroughly integrated into infantry tactical training and operations. And, most importantly to the scope of this article, both types were on hand and ready to go when the war in Korea began.

“Still, the companies will persist in carrying the 57mm [recoilless rifle forward in the hilltop fighting and will continue to use it futilely against targets which it cannot neutralize because of the distance, until at last they have one happy experience with the 75 on lower target ground against the same type of target. Then they adopt the weapon for good.” ORO-R-13

While there are numerous instances of recoilless rifles being used successfully against enemy armor, their most effective employment in Korea was undoubtedly in a long-range direct fire role against enemy defensive positions. North Korean and Chinese machine gun bunkers were a particular thorn in the side, hard to spot and even harder to take out.

Typically, these were deeply dug and reinforced with heavy timbers front and overhead so that only a direct hit from mortars or artillery would be sufficient to put them out of operation. Indeed, combat reports are full of frustrating instances where extended barrages, aerial delivery of bombs and rockets, and even smothering with napalm wouldn’t kill the dugout’s occupants.

But they were no match for the flat-trajectory and hard-hitting recoilless rifle firing on a line of sight from one ridgeline to another. Documented combat reports in ORO-R-13 unequivocally state that, “At ranges between 1000 and 1200 yards, the 75 recoilless is the only piece which can take them out under direct fire, with a relatively good chance of hitting dead on and destroying the object in one round; pack artillery might do it if it were available, but in its absence, the recoilless weapons are the main hope.”

Primary References

FM23-81 and FM 23-32 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