I know that helmet technology has come a long way and helmets can protect you from all kinds of impacts, but are there any that are bulletproof? Is there a helmet maker out there lining its lids with kevlar or anything?
No. Motorcycle helmets are not bulletproof. They are not bullet-resistant, they will not help deflect a bullet, and they offer no protection from gunfire whatsoever. The only way a helmet will ever protect you from a bullet is if someone threw one at you.
A bullet is made of metal and travels at over 1,500 miles per hour on average. The actual impact force of a bullet is infinitely variable due to distance, caliber, power of the gun it is fired from and other factors, but you can expect anywhere from 200 foot pounds to over 600 foot pounds of force concentrated in an area the size of a dime. A motorcycle helmet is made largely of plastic, fiberglass, high-density foam, carbon-fiber, or any combination of those materials. Long-story short? Your helmet is no match for a bullet.
Even military helmets do nothing for bullets. There is one helmet that allegedly stopped an AK-47 shot once, but that helmet is not used widely and isn’t really feasible due to its weight. Military helmets are actually used as protection from shrapnel and falling debris. They’re even helpful for overhead door frames and protruding instruments and objects inside tanks—but not bullets.
There are many reasons to wear a high-quality, well-made motorcycle helmet. They look cool and they help reflect your personality for one. As an added bonus, they greatly reduce your chances of suffering a traumatic, even life-ending, brain injury should you crash your motorbike.
Helmets don’t so much offer protection from an impact as they do slow down deceleration. Think of a helmet more like a trampoline or a gymnast’s mattress than a shield and you’ll be closer to the right track. Effectively the hard outer shell helps dissipate forces across a greater area, while the inner material compresses and absorbs the shock. A gunshot will simply pierce both layers instantly.
So, long story short, helmets are not bulletproof and under no circumstances should you test to see if they are.