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Although designed to be mobile, the 120mm
gun and its mount weighed
a total of 29-1/2 tons. That's a lot
of metal to move! |
120mm in what appears to be a
semi-permanent
emplacement in the Hawaiian Islands. |
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Looking for even heavier antiaircraft options,
the Army adopted a massive 4.7-inch gun around the same time it
standardized the 90mm antiaircraft gun. Eventually,
this larger piece was redesignated by its metric equivalent as the 120mm. This gun utilized a
motorized automatic fuze setter and rammer. The same directors
employed by the lighter nineties could also control the 120mm. Using the
M10 director (a version of the M9 adapted
especially for this gun), the 120mm M1 was
able to tap the accurate gun-laying abilities of the new generation
SCR-584 radar sets. The 120mm offered
increased range and a higher muzzle velocity, but had a slower rate of
fire than the 90mm guns..
Although this piece was
undoubtedly a powerful gun with a long reach and excellent fire control
devices, its bulk made it somewhat impractical for introduction in the
highly mobile theatres of World War II. The number of 120mm guns
produced was relatively small, and only a few made it outside the
continental United States or U.S. territories during the war. Thus,
the potent 4.7-inch/120mm gun fell to footnote status in the annals of
World War II antiaircraft artillery.
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120mm Antiaircraft Gun M1
firing circa 1945.
(Photo: Donald C. Tredennick
Collection at
the Military History Institute,
Carlisle, PA.)
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120mm Antiaircraft Gun M1 Facts
Firing
Table Muzzle
Velocity: 3,000 feet/second
Breech:
Semi-automatic
Maximum
Rate of Fire: 10-15 rounds/minute
Elevation
Limits: -5º to 80º
Recoil
Type: Hydro-pneumatic
Fire
Control Director: M7 or M10
Maximum
Effective Slant Range: 14,000 yards
Maximum
Effective Horizontal Range: 16,000 yards
Maximum
Vertical Range: 15,670 yards
Actual muzzle velocity was dependent on ammunition
used and environmental conditions. Maximum range was limited by
a 30-second timed fuze.
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When deployed, the 120mm
Antiaircraft Gun M1 was served by a section consisting of a gun
commander, a gunner with an eight man squad, and an ammunition chief
supervising two ammunition handlers - a total of thirteen men.
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Crew from Battery B, 755th AAA Gun Bn pose
by the breech end of their 120mm gun in Hawaii during September 1945.
The war is now over, as reflected in the smiles and relaxed expressions.
The 120mm gun was dubbed "Strato-Flak"
because of its ability to deliver AA bursts at high altitudes.
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This 120mm M1 gun, tied to a railroad flat
car, shows the profile of its traveling position at Norfolk, Virginia in April 1944.
Most 120mm guns, as this one, remained
stateside during World War II.
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Heavy Tractor M6 served as the prime mover
for the 120mm gun.
The 21-foot long, 38-ton tractor had a top
towing speed of 20 mph on a good, level road.
The M6 was also used as a prime mover for
heavy army artillery pieces, such as the 240mm Howitzer and 8-inch Gun M1.
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