M-65 (T-131) Atomic Gun

In 1949 the U.S. Atomic Energy Commission started the development of a nuclear device small enough that it could be incorporated into a 280mm caliber projectile. Shortly thereafter, the Picatinny Arsenal managed to integrate the W-9 15 kiloton warhead into a conventional 280mm T-124 projectile. In May 1950, work began to design a cannon that could fire the new nuclear shell, taking as a basis a 240mm gun created during a former project called T-1. In the late 1950 Watervliet Arsenal completed the design of the 280mm T-131 gun, and in the spring of 1951 the first prototype of the gun mounted on a 280mm Gun Carriage T-72 was completed. Finally, in October 1952 three complete guns were publicly presented at Aberdeen Proving Ground and then production began to complete 20 units until 1953.

M-65 Atomic Gun gallery and more info