In November 1947, the new prototypes (AK-47s) were completed. It used a long-stroke gas piston above the barrel. The upper and lower receivers were combined into a single receiver. The selector and safety were combined into a single control-lever/dust-cover on the right side of the rifle. And, the bolt-handle was simply attached to the bolt-carrier. This simplified the design and production of the rifle. The first army trial series began in early 1948. The new rifle proved to be reliable under a wide range of conditions with convenient handling characteristics. In 1949, it was adopted by the Soviet Army as "7.62 mm Kalashnikov rifle (AK)".