Not at all, I've had very good results with Fiocchi Exrema 77gr SMK.
And yeah most basic ARs are of the M4ish variety don't have freefloat handguards and 5.56 NATO chambers, but there are some available that have Wylde chambered stainless barrels and are free floated.
Was on PSA's site they have a 18" kit for $499 that should easily be MOA.
I used a cheap AR Stoner barrel $119 on sale for my optic service match build and it'll do sub MOA with the aforementioned Fiocchi ammo.