You want to be careful using the whitebox varmint stuff in military style semi-auto rifles. If the bullet catches on a feedramp you can have it setback in the case. The ammo is intended for use in bolt guns and is crimped appropriately. It needs a much heavier crimp if you prefer to shoot it in a semi. Otherwise, you risk excessive pressure, FTF, double feeds, basically a potential nightmare. I once made the mistake of attempting to shoot it in several of my ARE-15s. Not having shot an ACR I don't know if you'll run into the same problem, but forewarned is forwarded. Good luck.