Those who don't think a 5.56 will swiss cheese- as in the vaunted complete pass through, a car or pick up are really deluded. the SS109 ammo penetrates as deep as M2 ball in -06 or standard 7.62 ball does at 100 yards, the 5.56 does lose depth faster than the .30's. Even 9mm will penetrate car doors, a .45ACP 2 of them for sure, the issue with windshields is the slant, the more slant the greater the effective thickness is.
My back stop is 2.0" boiler plate and even .50 BMG ball does NOT penetrate it, nor the brass 650 and 700 grainers. .270 WSM 140 TSX's and .257 Bob 100 TSX's actually leave deeper craters than military ball ammo does.
