Bulletproof Helmet

How bulletproof? There’s a big difference between a helmet that will stop a .22 LR at 300 yards range and one that will stop 7.62x51 point blank. A sheet of 3/8″ AR500 armor steel will stop .50 BMG ball ammo at 300 yards. You could make a helmet out of 3/8″ steel, but it would be too heavy to wear. The current Advanced Combat Helmet gives NIJ IIIA level protection...