This is one of those ideas that you read about and it just makes you scratch your head. There are many different versions of ideas like this: the "is that really a good idea?"; the "no way"; and the "oh God, I gotta see this." Fortunately, the Davy Crockett fulfills all three of these particular categories. There are not a lot of surviving documents on the Davy Crockett today, unfortunately (or perhaps fortunately). However, I have compiled a limited quantity of information for posting here. It's an entertaining read that required a foreword, and will require some commentary from me afterwards as well. Enjoy!
The M-28/29 Recoilless Rifle
During the peak of the Cold War, deployment of nuclear arsenals was the staple of the military strategy. By and large, nuclear weapons were deterred with other nuclear weapons. This manifested mainly in the form of the deployment of nuclear capable bombers, warships, ballistic missiles, and eventually submarines. Early on, this also included short range weaponry, however. Projectiles such as the Honest John were deployed as little as 17 miles from their intended point-of-impact zones. However, the U.S. was experimenting with a more portable means to deploy these weapons than a predictable missile site. The result was the introduction of cannons and guns capable of firing an atomic round. This included the aptly named "nuke bazooka."
Developed in the late 1950s and then deployed in various regions as a means to contain communist regimes, the M-28 Davy Crockett weapon system was assigned in substantial quantities to various divisions in Europe and Asia. The primary deployment zones were in the still hot DMZ of Korea, and the uncertain and heightened risk area of the Fulda Gap.
Equipped with a bulbous atomic round at the front, the projectile produced a yield roughly equivalent to 30 tons of TNT. For comparison, the atomic bombings in Japan were 16-21 kilotons of TNT. The deployment of the weapon was not necessarily to create devastating damage by explosion, but rather to increase the amount of radiation across a target area. It was during this time that the use of radiation walls to prevent invasions were considered feasible. However, the apparent results of radiation sickness and affect on U.S. soldiers in the proposed plan became more apparent by the 1960s. With this revelation, the deployment of atomic weaponry for radiation walls was slowly culled and replaced with more intermediate deterrents.
Still, variations of the Davy Crocket continued with conventional weaponry, and the system continued operation in limited quantities through the 1970s. It is unclear exactly what changes were required to make the gun compatible with a conventional round, and most chassis modifications occurred on the gun itself, not the projectile. The last known firing of any Davy Crockett was in 1975, and the last known atomic round was in 1964.
Two versions of the Davy Crockett exists within the atomic and conventional typing: mounted and mobile. Both were technically mobile since the mounted version was attached to a jeep. However, the mobile version was able to be broken down into three parts and easily stowed for quick movement.
To put this into perspective for everyone: consider this literally to be it's unofficial name - a "nuke bazooka." As I have told people in lectures before, the Davy Crockett required two men to fire...somewhat successfully. Ideally, you'd select a day where the wind was blowing away from you. Your buddy would be in a jeep downrange and start driving towards you as fast as he could. Just before he reaches you, you fire the weapon. If you timed it right, you jump into the bed of the jeep as he drives by and you speed away. The weapon impacts. And you still get sick from radiation poisoning and probably die.
Thus is the tale of one of the...ickiest ideas we've had in our military weapons history.
If you find this system interesting, there are a few surviving examples. My favorite goes to the Atomic Testing Museum in Nevada, where the projectile is painted a hotrod red. Really gives it that "baboon's butt" look. Oy...