Helmets vs certain calibers

[Heatofbattle 49]

How much does wearing a helmet protect against assault rifle bullets and pistol rounds? I know they don't help much with the mosin but will they help me survive a headshot or two?

[Death By Crowbar 1213]

I know that the ballistic helmet and *maybe* that flight/jet helmet help against headshots, I was always under the impression that the rest didn't help much. I'm also curious if my understanding on this is accurate, and I'm also curious about which actually help in fist fights... the old rule of thumb was that moto helmets prevented against fist knock out but now with the other new things (bike helmet, work helmet, welding mask, etc) which actually help against headshots and which actually help against fist knock out.

[SwitchSL (DayZ) 17]

IIRC, ballistic helmets prevent 1 bullet from killing you. 

[BCBasher 2465]

I believe I read the gorka helmet cs stop a couple pistol bullets an melee knock outs with the visor.

[Tactical Nuke 47]

I have seen a video, can't remember who by, who was knocked unconscious from a headshot and when he woke up the only item ruined was his Gorka helmet w/ Visor.

[nexventor 429]

I'll just leave this here...

 

http://www.liveleak.com/view?i=a4c_1424034937