"During one of the tests there were three goats staked out in the open. Two in front of us and one behind. The first goat was the closest to ground zero. During this test the firestorm went right over us. When we raised up and looked around the two goats in front were scorched real bad and all the yucca trees for a long way behind us were on fire. Some of the ditches had caved in."

Cpl. Don Campbell, 412th Construction Engineer Battalion, US Army

So, the Soviet Union has enough tanks to roll through Western Europe almost uncontested, the Air Force is 40 years away from effective tank busting aircraft, and your NATO allies are literally screaming for more protection from the ravenous hordes of Communism camped just over the border. What do you do? Apparently, somebody at the Aberdeen Proving Ground was reading too many comic books. In late November 1949, the Chief of Ordnance, in compliance with instructions from the U.S. Army Chief of Staff, ordered design changes be made in the 280mm M65 weapon, which was already in development. It was modified to accommodate an atomic charge, namely the W-9 artillery projectile, an Oralloy (highly enriched uranium) fissile material shell. A nuke in a gun shell.

Supervillain secret weapons by order of Congress produced the 280mm M65 "Atomic Cannon", affectionately called Atomic Annie, which rolled off the assembly line on October 15th, 1952. Truly, the M65 was the strangest weapon that the Ordnance Corps of the Department of the Army ever produced. It filled an important deterrence role in the tactical nuclear arsenal of continental Europe when it was deployed in 1957 with the 7th Army’s' 3rd Armoured Division by way of attached units from V Corps, serving in West Germany. A total of twenty cannons were built. Of those, about ten to sixteen where deployed. The M65 remained in service until 1963.

The completely mechanical and hydraulic design allowed the M65 to fire a 600 lb. shell up to 18 miles. No electronics were used in the operation of the M65. Deployed as a tactical nuclear defensive weapon, it could fire the T-124 conventional high explosive shell. The M65 was also semi-mobile, and could be set up and ready to fire within 8 minutes. It required two dedicated tractor-trucks, which were attached at the front and back of the gun carriage to push and pull it into firing position. If battle damage disabled the gun's hydraulics, it could be aimed manually by turning geared wheels, but it was loaded by a hydraulic power rammer. One cannon, including transport vehicles and a separate armoured ammunition carrier, required a total crew of 22. The recoil from firing 600 pound shells was absorbed by dual recoil buffers, one of which separated the barrel from the upper carriage, the other separating upper and lower carriages. 90% of the 50-ton gun weight actually recoiled. To discourage enemy infantry, each transporter was fitted with a .50 cal. Browning machine gun. Better safe than sorry.

Thankfully, the M65 was never fired in anger. The W-9 atomic artillery shell came in 3 yields, and the maximum lethal range of the shell was dangerously close to the 18-mile range of the M65. 80 W-9 shells were produced from 1952-53 for the T-124 280 mm shell. A W-9 shell was fired as a part of Operation Upshot-Knothole, a series of atmospheric atomic tests performed in Nevada during 1953. On May 25, the test named GRABLE saw the M65 fire a 15 kiloton W-9 shell 7 miles into the Fulda gap, a natural feature in the desert at Frenchman Flat, Nevada. A mock town complete with buildings, roads and used cars was constructed at target ground zero and soldiers occupied trenches less than 5 miles away. Hundreds of high-ranking Armed Forces officers and members of Congress were present, anxious to see their new toy in operation. The shell detonated 524 ft above its target in a timed airburst.

It was the equivalent of the Hiroshima A-bomb.

Seven M65s survived the Cold War and are on public display today. The largest atomic cannon sits in a public park in Junction City, Kansas, on permanent loan from the Smithsonian. Another can be seen at the National Atomic Museum in Albuquerque, New Mexico.


The original specifications as produced by the Army are presented below:

GENERAL

Purpose: To provide a highly mobile long range artillery weapon.
Weight: 166,638 Lb. (carriage and transporter units), 94,000 Lb. (emplaced)
Length: 84'2" (traveling position), 38'5" (emplaced)
Height: 12'2" (traveling position)
Distinctive Characteristics: Rectangular carriage, large circular firing base near front of carriage, rectangular float at rear of carriage and two recoil mechanisms.

GUN

Type: Field.
Length: 42'9".
Muzzle Velocity: 2,500 f/s.
Range: 18 Miles.
Rate of Fire: to be established.
Firing Mechanism: (firing lock T95) electrical contact.
Breech: Step-thread, interrupted screw.
Ammunition: Separate load high explosive.

CARRIAGE

Type: double recoil, ball and socket traverse.
Traverse: 7.5 degrees (fine), 360 degrees (by moving float).
Elevation: 55 degrees maximum.
Recoil Mechanism: hydro-pneumatic (M32 and M33).
Sighting Equipment: (on carriage) elevation quad M1A1; pan tel M12A7C; tel mount M30; gunner's quadrant M1A1; quadrant adapter M10; setter fuze M26 or M27 and M28; (off carriage) aiming circle M1 with equipment; B.C. tel M48, with equipment.
Pertinent Equipment: generator (power sources) for elevating gun and ramming projectile.
Prime Mover: Transporter, heavy artillery T10, consisting of truck M249 (front), truck M250 (rear), and Carriage M30.

References:
http://www.designation-systems.net/usmilav/nuke.html
http://en.wikipedia.org/wiki/Nuclear_artillery
www.3ad.us/history/cold.war/nukes.pages/ atomic.cannon.htm
www.roadsideamerica.com/attract/KSJUNatomic.html
Nuclear Choices - Wolfson

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