My example was just a bog standard 8mm John Inglis Chinese contract Mk II Bren with the magazine adapter/ejector block, AK magazine, and the chamber sleeved and rechambered to 7.62x39. The painted markings on the butt translated to Navy (Peoples Liberation Army, Navy). I never shot it and sold it a few months ago to a specialised ChiCom collector. The piston and bolt were unaltered except for an ejector clearance cut in the upper rear surface of the bolt. I assume they just used the larger gas regulator holes for reliable operation.