I went with the 22/45 then started adding parts done the trigger and the hammer bushing and comp first. Then I ended up putting a loaded chamber indicator delete, firing pin, and extractor and with those mods it will run any standard or higher velocity ammo. My thought was if I wanted to add another top end later I would have a good trigger in my lower but so far I haven't seen a need for a new top end. It does fine for the two steel matches we shoot a month