Comparing: Centurion Action X vs. 121

The Action X turret was planned to be used for later variants of the Centurion tank. One prototype of the turret was mounted on the chassis of the Centurion Mark 7, and another was used for ballistic trials. The vehicles with the Action X turret never entered mass production or saw service.

Development began in 1962 on a new medium tank based on the Type 59. The new tank was expected to feature improvements in firepower and armor protection. However, the project was canceled shortly after. Some technical innovations were applied later, in the development of the Type 69 tank. All 121 tank prototypes were destroyed during Chinese nuclear weapon testing.