"The Atomic Cannon, at 280 mm, was the largest nuclear 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. Twenty 280 mm cannons were manufactured. None were used in battle. "
"The Atomic Cannon, an M65-280mm, is 42 feet long and weighs 42,500 lbs. It can throw a shell 20 miles, which would place ground zero southwest and just shy of Abilene (home of the Eisenhower Museum and the Hall of Generals)"