The AO-63 (Russian: Автомат АО-63) is a Soviet two-barrel AK derived assault rifle chambered for the 5.45x39mm round. It was designed by S. G. Simonov and P. A. Tkachev, and manufactured by TsNIITochMash. It uses a side by side barrel configuration, and it can reach a maximum rate of fire of 6000 rounds/min when fired in two round burst mode with a 0.01 millisecond delay to increase ballistic performance, making it the fastest firing assault rifle known.
The AO-63 assault rifle was used by the Spetsnaz during the Abakan trials in May/June 1986, in search of a more accurate alternative to replace the standard issue AK-74. It was described in the official report as being highly accurate as well as simple and reliable; despite its accuracy and performance, it was later dropped out of the competition for unknown reasons, with the AN-94 emerging victorious.
The AO-63 is a gas operated, 5.45x39mm calibre, twin barrel assault rifle derived from the Kalashnikov rifle. The weapon has side by side barrels with the right barrel predominant, twin rotating bolts/gas pistons and ejects from both sides. The trigger group has a 3 position selector on the right side of the receiver, the first is semi auto firing one barrel, the second in full auto firing both barrels with a 0.01 millisecond delay, the third is unique as at first it fires a two-round 6000rpm burst then one barrel in 850rpm full auto. The magazine is unusual as it has the main double column holding 30 rounds with a single column holding 15 rounds.
