7.62 will go through both sides of an issue ballistic helmet. high-speed low-drag all the way.
kevlar is only effective when allowed to flex and stretch to "catch" a bullet, which doesn't work so well in a ridged helmet.
i have seen many videos from Iraq/Syria of western soldiers being killed while gunning in a hummer, with the majority of shots going through the kevlar helmet.
Weapons Technician / Gunsmith
Don't look at me, I don't know, lol ¯\(°_o)/¯.