Adam, I kinda thought so. Even a 4 mil bolt 'buttom' tapped out would have a shallow seat for screwing not to mention it could put unwanted pressure over the bolt and breech. Still a super nice job though!!! Is that QB your looking at a repeater?!? I've heard co2's can freeze up if shot consecutivly at a frequent rate. Big Cats never freeze up!!!! LOL's I'll admit, I've been looking at the crossman .22 co2's for my short-range 'urban' rifle. Two .17 cal springers are enough for me, (got three and the BC's on the for sale list) and I'm like you,...rather spend the money on a different gun. But a nice CB9 would complete my pumper collection!!!! Good Luck, your pal, Thomas