 The Colt 2000's internal workings were based on older firearms designs from the early twentieth century.The rotating barrel, for example, was based on that of the Steyr 1912 and the roller-locking mechanism was based on a design used by the French "Manufacture d'Armes et des Cycles de Saint-Etienne" since 1914.These features allow the barrel and slide to work as a unit moving to the rear until the barrel lug rotates into the cam-block and stops.