Yeah right, it just says 9mm and muzzle velocity, aaaaaaand the "music" in the background tells you right away.....DON'T BELIEVE IT. Whats the weight of the Bullet? Which Material is the Core made of? Questions over Questions over Questions. Lab? Really?? Did you know that the Brasilian Wandering Spider makes you gonna Fuck all Night long? everyone let them self get bitten by this Kind of Spider, because it's a Natural and very Strong Viagra like Venom. Dont believe the Industry that said, its gonna Harm you.
keep in mind the helmets that look like this were mostly used in the ww2 and probably some wars after that but largely in ww2. they weren't designed to stop bullets but instead minimize shrapnell damage : ) the helmets nowdays with multiple layers of kevlar and metal parts are designed to stop more than shrapnell. like small arm ammunition. but the moment there's something powerful like an assault rifle. that helmet wont do much as the energy significantly increases.
You forgot that Diamond is like glass... It's super solid but the bigger it gets the more brittle it get. That diamond helmet would of shatter like glass