Please do not get a .223 because you have a bunch of cheap ammo. The gun won't shoot well with it in most cases. 2MOA and sometimes 3MOA would be fairly common for that stuff. 1MOA and below you will need higher quality ammo. To get to .5MOA and better, 1) you need good reloads with premium bullets or premium ammo (eg, Federal Gold Medal Match might do it) 2) the rifle needs to be one of the better ones (yes, each one off the assy line is different) 3) YOU need to be able to shoot that well. If you are used to AR's and blasting at soda cans or deer hunting accuracy, you will need to step up your game.

And, yes, the 1:9 twist will shoot 77gn Sierra Match Kings just fine. I use them all the time in my Axis with a 22" barrel. And, yes, my cheap Axis with a Boyd's stock will shoot 1/2MOA IF I do my part. It did take around 400rounds to settle down to that kind of ability.

PS yes, there will be some people who say they can get tiny groups with cheap ammo/bullets. It is not the norm.