I have a 1322 and I bought a 15" barrel, Flat top piston/valve installed and the exhaust port is opened +24%. Installed is a stock breech and a pass thru bolt. I have an Alchemy Air Werks Rp valve. I have the Mellon Long probe bolt and Pass thru bolt. I'm going to try Over time to do every variation. FT w Long probe vs pass thru, I have a 15 and the factory 10.1 barrel and I have the port opened up 25%. I'm going to Chrono and swap parts and see the best fit for accuracy. Still need to work on trigger but I have it nice and a lil light. The sheet is a 3 sho per t quick Chrono of my guns.