The T131 280 MM Heavy Motorized Gun

The T131 heavy motorized gun was the experimental model of the M65 atomic cannon.  Adopted in 1956, the cannon could fire both nuclear and conventional shells over a range of 18 miles.  Rendered obsolete by the development of more mobile rockets, the atomic cannon was withdrawn from service in the U.S. Army by the mid 1960s.  Only 8 cannons remain today.  The cannon weighs about 47 tons and is mobile.  The prime mover consists of both a front and rear truck that can reach a maximum speed of 30 mph.

"Atomic Annie"

Atomic weaponry was the staple in military arsenals during the Cold War.  During the early onset of the arms race in the 1950s, atomic warheads were not yet being fitted on missiles, but rather appeared in the form of freefall bombs.  For the U.S. Army, however, where military tactics included the use of atomic weapons on and close to the front line, a weapon was designed to deliver an atomic artillery round behind the front lines.  The demand for such a weapon led to the development of the M65 280 MM Motorized Heavy Gun, also known as "Atomic Annie" or the Atomic Cannon.

Based on the "Anzio Annie" gun developed by the Germans, the T131 280 MM Gun was developed at Watervliet Arsenal in 1950 with the intention of loading it with a W-9 15 KT atomic projectiles (T124).  The T72 Gun Carriage was used to cradle the gun.  Two 4x4 semi-trucks were required to move the gun into position.  The truck at the front was designated the M249, while the M250 was the truck at the rear.  Both were manufactured by the Kenworth Truck Company.

The first tests took place at the Aberdeen Proving Grounds in 1952.  However, the first and only atomic round to be fired from one of these cannons occurred on 25 May 1953.  Codenamed shot "Grable", the testing was part of the Upshot-Knothole atomic tests.  It took place at the Nevada Proving Grounds and the detonation of the warhead occurred at an altitude of 524 feet (above the target area).

With twenty guns produced, only a few have survived.  This includes the cannon at Rock Island Arsenal, Fort Sill, Oklahoma, and Fort Riley, Kansas.  The specimen at Fort Sill is the cannon which fired the atomic round during the "Grable" Shot.  The only complete cannon system known to remain is at the Aberdeen Proving Grounds.


The Atomic Cannon is a marvel to everyone who has gotten a chance to see her.  Based upon the Anzio Annie, a 283 mm Axis Germany gun, Atomic Annie was a 280 mm monster capable of firing large atomic shells.  She was the first, but not the last.  Upon her retirement in 1963, smaller howitzers and guns took up the mission of using atomic-tipped shells.  This continued until 1992, when all atomic shells were removed from U.S. military inventory.
The T131 gun is only a piece of the entire M65 assembly.  Included in the entire assembly is the T72 carriage along with the M249 and M250 prime movers.  Only one complete system remains, with the rest being just the T131 gun and T72 carriage.

Quick Facts & Specifications (M65)

Weight: ~173,000 pounds
Dimensions: 84.0' L, 16.1' W, 12.1' H (Towed)
Firing Range: ~7-20 miles
Caliber: 280 mm
Yield: 15-20 kilotons (Adjustable)
Crew: 5-7
Variants: 3 (1 Production, 1 Derivative, 1 Prototype)1
Number Built: 20
Origin: United States
Service History: Prototype, 1946
Production Starts, 1952
Atomic Testing, 1953
Production Ends, 1957
Retired, 1963


Area of Operations


1 Of the three variants, only one was the production 280 mm.  One was the predecessor T1 testbed, while the other was the 175 mm successor.
* The gun is listed as a prototype, however this is loosely the case.  The T1 was the testbed that was used later in 1949 for what became the M65.  It was not part of the same program originally.

Leave a Reply

Your email address will not be published. Required fields are marked *