I just put together a 2240 with a 14.5 and a Boss valve, extended probe, and I opened and polished the transfer port up a bit.. I put in a heavy spring but was getting horrible shot count so I went back to a stock spring with a spring guide waste of co2 I think. It was raining all day so I did not get a chance to chrony it yet. I'm not looking for a hunting gun, just a nice plinker for indoors this winter. I was getting a sold 18-19 shots with a .75 inch group at 30 yards with a red dot mounted. I have been using the Lealand 12g cartridges and JSB 13g RS pellets. Its my first 22xx build and Im having a blast with it. If I was not saving up for a TX200 I'd plop down the money for a Crosmods breach and shroud. Oh ya and my new TKO on it is very nice.