The author’s introduction to the “fifty-cal” was the opportunity to fire a few rounds for familiarization during infantry training in 1967. That was after we had been shown the basics of its operation: how to load, cock, fire, and clear it. Such was the extent of our exposure to the legendary “Ma Duce,” officially known as “Machine Gun, Caliber .50, Heavy Barrel, M2.” The instructor explained that the M2 had been in use since 1933. Some of the trainees, including myself, gazed curiously at the guns placed before us, thinking that they didn’t look that old. In fact, the ones we were training with had been manufactured during the Korean War (1950–53). Our introduction to the “fifty” was minimal, as infantrymen did not generally operate the weapon – M2s were typically found in headquarters and support units, mounted on trucks for self-defense, while in mechanized and tank units they were set atop armored fighting vehicles (AFVs). In addition, each self-propelled artillery piece possessed a “fifty.”
   I discovered more about the .50-cal during subsequent Special Forces training, learning to disassemble the monster and gaining a little more experience in firing it. Yet it was in Vietnam, with some hands-on experience, that I truly learned to appreciate the “Number 50” as the Vietnamese called it. (They also called it the “M50,” along the lines of the 7.62mm M60 machine gun.) Observing a US mechanized rifle company “trim the tree line” with a dozen “fifties” made me appreciate that the receiving end of such fire was a place no-one would want to be. Many Special Forces camps had no .50-cals, but others had up to four or more. Ours had two. One was mounted atop a 12ft “Medal of Honor tower,” so called because to climb up there during an attack virtually guaranteed you one. The other M2 was atop an inner perimeter bunker. Both were high enough to fire over the barracks on the outer perimeter and into the wire. The tower gun provided 360-degree coverage and the gun on the bunker protected the northern perimeter, the most likely sector to be attacked.

Armorers carry six M2 fixed machine guns and their ammunition to a P-51 Mustang fighter. Guns were removed after each mission for thorough inspection, cleaning, and parts replacement. (Cody Images)

   We never actually needed the M2s to defend the camp from humanwave attacks, for which they were originally intended, but they were used for harassing and interdiction on an infiltration trail system a few kilometers from the camp. We liked to think we sometimes made nights more “exciting” for infiltrators tramping down the trails. There was once much consternation from our B-team’s S-2 (intelligence officer), after a little Popular Force (local militia) outpost was overrun one night. The Military Assistance Command, Vietnam (MACV) advisors had given them a .50-cal, against the recommendation of our S-2, and it fell into the hands of the Viet Cong (VC). Indeed, the VC goal was not so much to neutralize the outpost, which they successfully did, but to capture the .50-cal. They wanted it bad enough to sacrifice several men. As a result, US/South Vietnamese helicopters in the area had to be more cautious – since among the .50-cal’s many varied capabilities, it can be a very effective antiaircraft weapon.
   Witnessing the downrange effects of the .50-cal bullet is an eye-opening experience. Bullets punch right through 14in- and 16in-diameter trees, crack through cinderblocks, penetrate two sandbags and foxhole parapets in one go, and hole 1in-thick armor plate, and that was just the standard ball round. There are few who can say they were “wounded” by a .50-cal. Those hit seldom say much more.

Three soldiers of the 62nd Coast Artillery Regiment (Antiaircraft) manning a .50-cal M2 watercooled gun mounted an M2 antiaircraft mount and fed by a 200-round M2 “tombstone” ammunition chest. A full chest weighed 87lb. (Hulton Archive/ Getty Images)

   The M2’s reliability is also legendary. There are three main causes of .50-cal failure: the operator failing to set the headspace and timing properly after changing the barrel; a part breaks – the M2 is a mechanical device after all, but the parts are so robustly designed that such failure is a rarity; or the gun is hit by enemy fire.¹ It is said that John M. Browning (1855–1926), the gun’s designer, produced a freehand drawing of the parts on wrapping paper for his machinist. The machinist asked how thick each portion of the part was and Browning replied by indicating a size between his thumb and forefinger. The machinist measured the distances with calipers and all the parts miraculously fitted together within the receiver’s confines as the prototype gun was built.
   On the back of this reliability, the Browning .50-cal M2 has become the longest-serving weapon in the US inventory. It first entered service in 1933, is in use today, and it will remain in use for many years to come. Earlier standardized versions date back to 1921 and the prototype itself to 1918. Since then, the M2 has been employed in every imaginable role for a machine gun – antipersonnel, anti-material, light antiarmor, antiaircraft, aboard aircraft as both defensive and offensive armament, as defensive armament on armored and soft-skin vehicles, as a ranging gun, and it has been mounted on naval vessels from patrol boats to battleships. In addition, a large number of variants have been developed, discussed in later chapters.
   The M2 is considered such an effective and reliable weapon that few countries have ever attempted to develop an equivalent weapon. Instead, it is used worldwide by literally dozens of nations. The British, for example, designated it as the L1A1 and L1A2 12.7mm (.50in) Heavy Machine Gun (HMG) with the Manroy Engineering quick-change barrel, the L111A1, while tank-mounted versions, the L6A1 and L21A1, were used as ranging guns before the advent of laser rangefinders. Before NATO standardization called for metric designations, the British referred to the M2 as the 0.5-inch Browning. In Germany it is known as the MG50-1, Israel as the MAKACH (Miklah KAliber CHamisheem = machine gun caliber fifty), Egypt as the DOBSH, Denmark and Norway as the m/50, Netherlands as MIT-12.7, Portugal as the m/55, South Korea as the K6, Sweden as the Tksp 12.7 (Tung kulspruta = heavy machine gun), Switzerland as the MG64, Taiwan as the T90, and Thailand as the Pkn. 93. Many countries simply retain the M2 designation. To date, an estimated three million Browning .50-cal machine guns have been made by different producers worldwide and it will be in use for many years, if not decades, into the future. From the aerial dogfights of World War II to the .50-cal-mounted Humvees in Afghanistan at the time of writing, the .50-cal has seen service in virtually every theater and every war since it was first designed.

¹ Headspace is the distance between the face of the bolt and the base of the cartridge case when seated in the chamber. Timing is the adjustment of the gun so that firing takes place when the recoiling parts are in the correct position.

The making of a legend

The principal development phase of the modern M2 machine gun began in 1918, the last year of World War I, and extended into the early 1930s. In one sense, however, its development story has never really come to an end, as existing models are continuously improved and new variants fielded right up to the present day.
   Development of the .50-cal round began in April 1918, when General John J. Pershing requested that a large-caliber machine gun be developed for use against tanks, aircraft, and long-range targets such as far-off enemy artillery crews. Indeed, the cartridge was developed before the gun. The need for such a weapon was first called to the attention of the Ordnance Department by Lieutenant Colonel John H. Parker, the same “Gatling Gun” Parker who as a lieutenant commanded the Gatling Gun Detachment in Cuba in 1898. It was while he was touring a French machine-gun school (rather than commanding a US machine-gun school in France, as is usually reported) that he was introduced to their 11 x 59mmR Gras (.445-cal) Hotchkiss aircraft machine gun.¹ This round provided a more effective incendiary bullet than US .30-cal bullets. Parker was also shown an experimental 12mm (.472-cal) Hotchkiss anti-balloon gun. He obtained one of these guns and shipped it to Frankford Arsenal, Pennsylvania, where he conducted performance testing on the French rounds. Both the 11mm and 12mm rounds, however, lacked the necessary range and velocity desired by the Army. Pershing, or his ordnance officer, had specified a muzzle velocity of 2,600 feet per second (fps) with a 670-grain bullet. The Army requested that Colt convert eight .30-cal M1917 water-cooled guns to 11mm ammunition for testing, but this configuration proved unsatisfactory.
   An alternative route was explored by the firearms manufacturer Winchester. It immediately began work on a new cartridge, a scaled-up .30-cal but with a rim, and referred to as the .50-caliber High Power. At the same time, Winchester was also developing a tripod-mounted, repeating antitank rifle chambered for the cartridge, the bolt-action M1918. The Army preferred a machine gun, however, as both an antiaircraft and a general automatic weapon, the machine gun being perceived as more effective against tanks and long-range targets.
   Another discovery of testing with the French ammunition was that the French rimmed 8mm and 11mm rounds were less than ideal for machinegun belt-feed systems. Consequently, both American Expeditionary Force and Ordnance Department officers felt a rimless round would function better. The prototype was finally developed in June 1918. Yet it was still not firmly established that the new .50-cal would be rimless. Rimless, semirimmed, and rimmed cases were all still being tested into the early 1920s, along with scores of different bullet weights and designs, and propellants. Different case lengths were also tested. The 3.89in-long rimless was finally settled on in 1921, but the first officially adopted ball round was not standardized until 1923.
   In July 1918, John Browning at Colt had commenced work on scaling up the .30-cal M1917 machine gun to handle the .50-cal rimmed, producing the Colt Mk 50. As a result the water-cooled M1917 can be said to be the father of the .50-cal. Its grandfather was a design Browning had originally developed in 1900, but an actual prototype was not built until 1910, as Browning was preoccupied designing sporting rifles, shotguns, and pistols.

A .30-cal Browning M1917. The water-cooled version of the M1917 was said to be the father of the .50-cal, as Browning used a scaled-up version of the .30-cal as the initial basis of his design.

   In early 1918, German 13.2 x 92mmSR (.525-cal) antitank rifle cartridges were obtained. This round kicked out a whopping 800-grain steel-cored bullet at 2,750fps, capable of punching through 1in of armor at 250yds. This German round had been originally used in a massive 35lb, 66in-long single-shot, bolt-action, bipod-mounted Mauser antitank rifle called the Tank Abwehr Gewehr Mod. 18 (Tank Defense Rifle Model 18, or T.Gew. – “T-rifle”). The round, often simply called “13mm,” was also to be used in a scaled-up Maxim MG08 watercooled machine gun, the MG18 Tank und Flieger (T.u.F.) Maschinengewehr (MG18 Tank and Aircraft Machine Gun), intended as an antitank and antiaircraft weapon.

   In response to studies of the German round, modifications were made to the US .50-cal round under development, these modifications being conducted in great secrecy – the Ordnance Department did not want it known that German ammunition was considered superior to American. In November 1918, it was decided that further development of the .50-cal round would be undertaken at Frankford Arsenal, although Winchester continued to produce test lots into 1919.
   In late 1918, Winchester sent a dummy rimless round to Browning, allowing him to modify the Mk 50 gun from its previous rimmed configuration. Browning took the gun to Winchester for single-shot test firing, to optimize the loading for velocity and reduce the strain on the gun. This cooperation sped up the development process and Browning stayed on at Winchester. In September, the first gun was ready and six more would be built. Six Browning air-cooled .50-cal aircraft guns were also completed, being built by Winchester after modifying Browning’s water-cooled design. Browning accomplished the development of the .50-cal machine gun and its ammunition in just over a year, as well as simultaneously handling several other important design projects, including the M1918 Browning Automatic Rifle (BAR), .30-cal M1917 heavy, and M1918 aircraft machine guns.
   The first full-automatic test firing of both the water- and air-cooled guns was on November 18, 1918. The newly assembled gun fired about six 100–150-round bursts for a total of 877 rounds at a cyclical rate of 550 rounds per minute (rpm) without a stoppage. The Ordnance Department immediately recommended that 5,000 each of the water- and air-cooled .50-cal M1918 Brownings should be ordered from Winchester. Interestingly, both the T.u.F. MG18 and the US .50-cal M1918 were developed at the same time, both being scaled up from their country’s standard rifle-caliber water-cooled machine gun, intended for the same roles, and both were to be fielded in 1919.

John M. Browning himself test fires the first .50-cal water-cooled machine gun in 1918. The gun and tripod were basically a scaled-up .30-cal M1917 Browning, which remained in the Army inventory into the early 1960s. (US Army)

¹ Metric cartridge designations are often comprised of the approximate caliber in millimeters with the second number being the case length. Rimmed cartridges are further identified by an “R,” semi-rimmed rounds by “SR,” and belted cartridges (which feature a reinforcing band above the extraction groove) by a “B.” Rimless cartridges have no letter identification.

The American gun still did not quite meet the US Army’s requirements, however. The 707-grain bullet flew at 500fps less than desired by Pershing, only 2,300fps. The prototype guns had only a 30.5in barrel, as this was the longest barrel that Winchester could rifle. An adjusted propellant charge and longer barrel would provide the desired velocity and increase the range. (The .50-cal barrels are rifled with eight lands and grooves with a right-hand twist with one turn in 15in.) Additionally, the infantry found during subsequent trials that the gun was difficult to keep on target, as it rose considerably during firing if not locked in position. But if locked it was almost worthless against moving vehicles, much less aircraft. Moreover its 160lb weight (the weight of the gun with 8qt water and tripod) limited its battlefield mobility, especially in the offense. As an antiarmor, tank-mounted gun, it was also found to be less than optimal. Even Pershing’s velocity requirement was insufficient to make it effective against newer tanks, and the bullet was too light. In addition, its rate of fire was too slow for antipersonnel use, but a higher rate of fire was punishing to the weapon. Just because both the cartridge and weapon were equally scaled-up from their .30-caliber predecessors clearly did not mean that the gun could handle the brutal recoil. The order for the M1918 was cancelled at the war’s end, but further development was undertaken to improve the gun and its ammunition.

The first standardized .50-cal Browning was the M1921 watercooled antiaircraft machine gun with a 36in barrel, here on an M1 AA tripod. It can be seen how the legs hampered the gunner when tracking a highspeed aircraft. It is fitted with a 200-round M2 “tombstone” ammunition case. (US Army)