BARS replaces a traditional gas piston system,  named after the creator of which weapon?
AL-7 The AL-7 is a Russian assault rifle designed by Izhmash engineer Yury Aleksandrov in the early 1970s. The AL-7 uses a type of operation developed by Pyotr Tkachyov of TsNIITochMash (Central Institute for Precision Machine Building) in the mid-1960s known as "Balanced Automatics" first used on the AO-38 assault rifle. The Balanced Automatics Recoil System (BARS) replaces the traditional Kalashnikov gas piston operating system, reducing the negative effects of recoil and allowing more efficient use of automatic fire. BARS works by shifting mass toward the muzzle of the rifle as the bolt and bolt carrier recoil rearward.
Gast gun The Gast Gun was a German twin barrelled machine gun that was developed by Karl Gast of Vorwerk und Companie of Barmen and used during the First World War. Its unique operating system produced a very high rate of fire of 1,600 rounds per minute. The same principle was later used as the basis for the widely used Gryazev-Shipunov GSh-23L series of Russian aircraft cannon.