Quite a few piston driven semi-autos vent excess gas from the op rod tube. Would a device that captures such constitute a silencer? What if used in conjunction with a traditional muzzle mounted silencer? My Steyr AUG, for example, does not suppress terribly well because of the report from excess gas released from the gas port after the op rod is driven back. Would a device to muffle this constitute a silencer? The AK comes to mind as well as a popular gun which vents quite a bit of excess gas.