I shot a friend's SCAR (coyote brown?) with iron sights and it shot very well. I have some experience with AR platforms so it was a welcome change. Low recoil, accurate, easy to manipulate, and no jamming or issues (we were firing military issue rounds).
One gripe I did have was that after about an hour of constant (but not overly aggresive) shooting, the fore grip got so hot that we had to put a towel over the hand guard just to shoot. In my opinion this is unexcusable. I have shot AR's much more aggresively and for a longer duration of time where this was not a problem. Yes the AR's got warm, but literally we could no longer shoot the SCAR without either gloves or a towel to protect our hands.
Other than that issue, I give it high regards. Unfortunately I have never shot an ACR so I can't speak on that.
Hope it helps,