By the mid-1950s, the idea of turret-mounting a partially rotating gun had emerged. The XM57 was developed according to this principle. A special feature was that the crew was located not in the turret, but in a cabin behind it, which meant that the turret's dimensions could be reduced. Loading was fully automated. The gunner would have aimed using cameras in the turret, but a periscopic rotating reticle was also planned for the top of the cabin. The commander's cupola would have been mounted with a remote-controlled AA gun in order to tackle airborne targets. The project existed only in blueprints.