Question: BARS replaces a traditional gas piston system,  named after the creator of which weapon?
Sentence (from "AL-7"): 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.
Relevant evidence: Yes