Stag arms

M4 cuts have nothing to do with BCGs. If your upper has m4 cuts, your barrel NEEDS m4 cuts because if it doesn't, there will be a nice flat part for bullets to hang up on when feeding. If your upper doesn't have M4 cuts, it's better if your barrel doesn't, but things are usually functional if your barrel does as the upper will jsut cover some of the m4 cuts.

Thanks! I've heard stuff about all that, someone told me that ALL AR barrels had M4 feed ramps, which didn't seem right to me. Glad you cleared this up, otherwise I may have ordered the wrong parts.