SBR 5.56 ammo selection: why the FBI's weight-retention standard falls short

SBR 5.56 ammo selection, argued against the FBI protocol: Boondock Ballistician responds to the TFB interview that named 64- and 75-grain as the only good weights for an 11.5-inch barrel, and argues the shortlist follows from how the bureau grades — penetration depth, expansion diameter and retained weight, scored for engagements rarely past 50 yards.