Bcn complete lower Seemed it over so over and over and may't discover the blem. Everytime I feel I uncover anything off, it is just oil smudges. Greatest guess at this point is scuffs on castle nut, or The 2 very small silver places during the flare in the magwell. https://bcm-lower45689.izrablog.com/29359033/facts-about-bcm-lower-receiver-revealed