I bought a Ruger American chambered in 5.56 not to long ago, mainly out of curiosity and to experiment with loading rounds high for caliber slugs. Ruger was under $500, and the twist is 1:8, which is fast enough for slugs up to 72 grains. The only things I did to it was to tune the trigger a tad and add an inexpensive scope.
So far, I like it. Short and light, and I like the fact that I can use M4 magazines. Still working on loads, but so far I can equal or better 1 MOA up to 300 yards, so long as the wind isn’t screaming.