You may very well be on to something, SVT28, and I will likely pick up a flat base plate to see whether it’ll allow for a ninth round, but what still has me puzzled is the missing 8th witness hole marked with a “9.” As clang444 pointed out, there are only 7 witness holes in my mags with the bottom one marked “8.” Just like every other standard 10xx mag I’ve ever seen, Screwball’s 9-rounder has 8 witness holes marked “2” through “9” with “9” being below the bump. My mag has only 7 witness holes marked “2” through “8” with no hole below the bump.