those are out of production and unless someone is willing to sell you their's i think you're out of luck sir. but to be honest, the price of that barrel kit (Ruger 90455) was overpriced when it came out. if you do find one be prepared to pay more than the $350 original asking price. you'd be better off getting a dedicated 300 Blackout rifle... (if you can find one of those right now and the price gouging gremlins haven't caught up with it)