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An
antiaircraft machine gunner on watch at a hastily constructed dirt landing
strip in Northern France, shortly after the Normandy landings.
This is the classic water-cooled Browning machine gun on the
common M2A1 mount.
Note the hoses running out of the pit,
around the duffel bag, and to the water chest on the left.
The top of the water chest is visible
behind the tool handle protruding from the near left corner of the pit.
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For close-in antiaircraft
protection, the Army utilized the standard .50 caliber Browning M2 machine
gun in either a water-cooled configuration or in a heavy barrel (HB) air-cooled version. Beyond the cooling method, there was little
operational difference between the guns. In the years leading up to
World War II, many Coast Artillery AA officers felt that the increased
speed and performance capabilities of modern aircraft rendered the machine
gun ineffective as an antiaircraft weapon. Experience in the war
would reveal otherwise, as the AA machine guns provided a potent defense
against both air and ground threats. Whether affectionately referred
to as "Ma Deuce" or "The Chicago Atomizer", the .50 caliber machine gun
was an indispensable part of the antiaircraft artillery arsenal.
"The .50 caliber machine gun has proven to be a
dependable, effective weapon against Japanese aircraft. This weapon
was generally credited with eliminating extremely low altitude attacks
against our installations by Japanese aircraft."
Lt. Col. Robert Totten, Air Corps,
South Pacific Area, 1942.
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.50 Caliber Browning M2 Machine Gun Facts
Muzzle
Velocity: 2,900 feet/second (M2 ammo); 2,800 feet/second (M1
ammo)
Breech:
Automatic (must be cocked before first firing)
Maximum
Rate of Fire: 600 rounds/minute (450 rounds/minute for HB guns)
Elevation
Limits: +10º to 90º (depending on
mount used)
Recoil
Type: Spring
Fire
Control: Individual Tracer
Maximum
Effective Slant Range: 600 yards
Maximum
Effective Horizontal Range: 1,800 yards
Maximum
Effective Vertical Range: 1,700 yards
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With the introduction of
carriage-based twin and
quad mounts for the heavy barrel fifties, single
mount water-cooled machine guns gradually became less common, but continued in use
for the duration of the war. The water-cooled guns could be attached
to a variety of
mounts. Perhaps the most common was the M2A1, which
was simply an M2 mount modified by the removal of a somewhat bulky tracer
control device. A two-piece attachable shield fashioned from 1/4-inch
armor plate was available for the M2A1, but was seldom seen in the field.
The M3 mount featured a more integrated shield plate and a trigger rack
with three pairs of hand grips to accommodate various firing elevations.
The gun was fired by rotating any one of the three left grips counterclockwise.
The M43, a more substantial fixed-location mount with heavier 1/2-inch
armor shielding, was also employed at some installations. The M43 was
designed to be bolted to a concrete slab or some other type of foundation.
The
machine gun mounts (with the exception of the older M1) could alternatively be fitted
with a heavy barrel, air-cooled fifty.
All mounts could easily traverse a full 360º
circle.
WORLD WAR II
AA MOUNTS FOR THE .50 CALIBER MACHINE GUN
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M2
mount showing tracer control
mechanism. 15º
to 68.75º elevation.
392 pounds (w/o gun) |
M2A1 mount.
15º
to 68.75º elevation.
370
pounds (w/o gun) |
M3 mount with front alinement
ring sight. 15º
to 90º elevation.
350 pounds (w/o gun) |
M43
mount bolted to a
slab. 10º
to 80º elevation.
725 pounds (w/o gun) |
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Shown here (at
left) is the M63, or Kochevar mount, standardized in July 1944.
It offered an even lighter AA machine gun mounting option. It was
used as an alternate ground mount for HB guns normally affixed to standard
vehicle mounts.
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The lightest .50
caliber machine gun mounting method for antiaircraft use involved
the M1 elevator cradle, which was an adapter for the M3 low
tripod ground mount used by the infantry. The M3 provided a
steady foundation while the adapter raised the gun to a level where
it could be elevated sufficiently to aim at aircraft. This
combination was often employed by the infantry, but it did see use
with an antiaircraft unit at Omaha Beach on D-Day morning. The
elevator cradle and M3 mount weighed a combined 140 pounds.
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Water-Cooled
vs. Air-Cooled Machine Guns
Machine guns will
overheat when fired for extended periods of time or in long bursts. Overheating first
degrades accuracy, then quickly renders a gun barrel unserviceable. To
reduce damage due to overheating, a water-cooled antiaircraft machine gun utilized
a water jacket that slipped around the barrel and attached to the
gun’s trunnion block by a threaded mount. The jacket
surrounded the barrel with approximately ten
quarts of water. A pair of hoses connected the water jacket to an
auxiliary eight gallon water chest.
During firing, a hand pump produced a flow between the water jacket
and the water chest, providing an effective means of liquid-cooling
the machine gun's barrel.
In contrast, the heavy barrel of an air-cooled gun helped resist
overheating, but only if firing was kept to short bursts. In
the event of overheating, the barrel of an HB M2 machine gun was
designed to be changed quickly and easily in the field by the
machine gun crew.
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"The .50 caliber machine gun has proven a most
excellent weapon against low-flying aircraft, and German attack aviation
appears to dislike it intensely. These weapons interspersed along a
column will force enemy aircraft to stay so high that casualties inflicted
by [the aircraft] will be negligible."
Major General Walton H. Walker, IV
Armored Corps, North Africa, June 1943.
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Protection on the move. A
water-cooled .50 cal machine gun on an antiaircraft unit's truck provides
air defense for this column traveling a desert road. A 40mm Bofors
gun is being towed. Note that the soldiers riding in the rear are
facing different directions. All are serving as lookouts. |
Antiaircraft machine guns could be manned by up to three soldiers.
The gunner (G) would be in command of the gun and crew, assisted by an
ammunition handler (AH) and a water chest operator (WCO). The expediencies dictated
by war often prohibited the availability of a full three-man crew.
The AA machine gun could be operated by two men, or by a solitary gunner (as in the photo at the top of this page).
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This illustration from field manual FM
4-155 depicts a
three-man crew serving a water-cooled
machine gun.
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Pre-war photo of machine gunner training at
Fort Sheridan, IL. Note how the M2A1's pedestal is sandbagged. A chute on
the side of the gun feeds links and spent cases into a canvas bag.
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Silhouetted against a wintry sky,
this antiaircraft machine gunner stands ready with an air-cooled HB M2
gun in an M3
mount. All mounts except the obsolete M1 could accept water and
air-cooled guns. |
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