These?
Prob chop just below one of the horizontal ribs and cut a groove on or just above the rib for the baseplate to latch onto solid.
May have to put a very slight bow in the baseplate to make snug or use a BFH
May end up being 19rd, 20rd, 21rd, who knows, really depends on where those horizontal ribs land.
30rd usually gets cut ⅛-¼" below the loaded indicator window just to give you an idea.
Actually have to chop longer on metal to allow for extra material to be formed into tabs for the baseplate
Send it and I will molest it in ways bubba could only dream about
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