It’s a second version Gemtech Mist (no vent port in the barrel). It’s unbelievably quiet. I can sit on the couch in my living room and shoot through the open backdoor at a target in the garden. The only sound is bullet hitting the target. My wife sitting at her desk directly above me in the same room doesn’t hear a thing as long as I use a brass catcher or hold the bolt closed. She can hear a spent case if it hits the wood floor, but not the shots.
Not to be too alarmist, but I'd be a bit concerned about shooting too many rounds; the gas isn't all that healthy.