If you're not reloading I'd go to my local gun shop and see what they have most of In terms of ammo. The usual suspects will be 223, 22-250, 243 and so on. If you are only going to lamping ranges anything more than a cumshot will be sufficient. I'm a big advocate of the .204 but you will get far more offerings in .223 and it will give you a chance to diversify your rifle if you want to go bigger or smaller in terms of grain weight or game. Maby look into 1-8 or a 1-10 twist if you can get it. Gives you the option to stretch the legs if you start to get the notion for longer ranges.