The helmets weren't intended to stop a bullet. Glancing rounds it might shrug off, and a small caliber round- say, a 9mm pistol round- could struggle to deal with it, but in broad terms those helmets were about stopping fragmentation, shrapnel and whatever other random crap gets kicked up in a fire fight.

Can a military helmet stop a bullet?

So the answer is an absolute YES! Bulletproof helmets are meant to protect the wearer against different combat-based threats such as fragments, gunshots, shrapnel, explosions, etc. However, a gunshot is not always from normal range during combat.

Is there a helmet that can stop a bullet?

Modern ballistic helmets provide different levels of protection. The levels are generally tested in accordance with the National Institute of Justice. The NIJ rates ballistic protection based on what rounds the item proved capable of stopping during rigorous testing. Levels III and IV will stop common rifle rounds.