The Atomic Cannon, at 280 mm, was the largest nuclear weapons capable mobile artillery piece manufactured by the United States. On May 25, 1953, a 280 mm cannon fired an atomic projectile a distance of 7 miles at the Nevada Test Site. The test known as "Grable," exploded with a force of 15 kilotons, similiar to that of Hiroshima. Twenty 280 mm cannons were manufactured. None were used in battle. Sequence from the HD version of "Trinity and Beyond - The Atomic Bomb Movie" available on blu-ray.