Are helmets bulletproof ?

[CAJW]

Riding dual sports in the 70's at Kettleman hills, we decided to leave our helmets at camp and go putting around (living dangerously) with naked domes. When we returned, we found my buddies full coverage Shoei had a .22 bullet hole in it. Pretty freaked out, we didn't wait around for any follow up shots and beat feet for Visalia. So, no they ain't bulletproof and glad my buddies' melon wasn't in it!

 

[Uncle Hud]

As several have stated, it's not the caliber, it's the powder load.

The kinetic energy that does the whip-ass on your steel plate (or kevlar helmet) is calculated as 1/2mv^2, where ...

m = bullet mass, and

v = bullet velocity.

Since the bullet velocity is squared, it's a far more significant contributor to the final energy "transferred" to the target than the bullet's mass.

The 5.56 mm (.223 caliber) bullet is a common military rifle caliber because of the gunpowder load behind the bullet. Since military folks are in the killing business, I think they probably did a lot of research on muzzle velocities and the like before settling on the 5.56 as their standard round.

And for all y'all that believe a .22 is not a "real" pistol, try shooting a cantaloupe at 25 feet -- a typical distance for self-defense shooting.

 

[Bounce]

Helmets were never meant to be bullet proof. They were designed to resist shrapnel and can be seen in the old WW1 Dough Boy and French designs with the flared brims. Artillery shells were set to air burst over trenches and take out opposition troops by sending shrapnel raining down from above. The flare in the brims increased the area of protection to the wearer. The bulky and hot vests of 'Nam were, again, for shrapnel (grenades, artillery, etc.) and wouldn't resist even the most common bullets of the day.

Bullet "resistance" would be more a accurate term even to this day. A glancing blow from incoming rounds can be deflected and so serious injuries can be minimized for certain cases. Others have already addressed that bullet resistance (even in vests) is only effective until met by a "better" bullet.

 

[Old Guy]

Yeah, I took the subject line tongue in cheek at the first post. But it's been fun

 

[Pterodactyl]

"1/2mv^2, where ...

m = bullet mass, and

v = bullet velocity."

And that's why a Abram tank can fire a depleted uranium penetrating rod out of a 120mm smooth bore cannon at a velocity of over 1 mile per second and it will penetrate 14 inches of steel on the front slope of a tank, thru the crew compartment, ammo rack and then thru the diesel engine and out the back.

Mass is great but velocity kicks arse.

 

[rogdeb]

Yeah, I took the subject line tongue in cheek at the first post. But it's been fun

It was tongue in cheek

Entertainment purpose only.

 

[HotRodZilla]

Yeah, I took the subject line tongue in cheek at the first post. But it's been fun

It was tongue in cheek

Entertainment purpose only.

I'm hoping we all knew that.

 

[Old Guy]

Yeah, I took the subject line tongue in cheek at the first post. But it's been fun

It was tongue in cheek

Entertainment purpose only.

I'm hoping we all knew that.

Can't help wondering sometimes

 

[Uncle Hud]

If helmets were bulletproof, the Sons of Anarchy would've worn full-face models.

 

[rogdeb]

Good one ^^^^

 

[rogdeb]

Yeah, I took the subject line tongue in cheek at the first post. But it's been fun

It was tongue in cheek

Entertainment purpose only.

I'm hoping we all knew that.

All I know for sure is that I new that, as well as you Zilla, and OldGuy - LOL

 

[Bill Lumberg]

I have about half a cup of experience in this area. Not regarding helmets, but with the penetration of various rounds against various building materials, body armor, etc. I won't put too many specifics in a public forum, but I'll point out that charge and barrel length (and resulting muzzle velocity) have more effect in penetration than round diameter alone. For a non-deforming substance to resist a decent sized round, it has to be quite dense and/or thick. Traditional br fabric requires many layers, and uses deformation to avoid puncture (think catcher's mitt). For soft armor, backface deformation control is key (to limiting trauma). Traditionally, testing for soft armor is done using Roma clay.

 

[Bounce]

And we know that clay is heartier than torsos.

+level trauma plates exist for a reason.

 

[El Toro]

We used to shoot into ballistic jelly to see how well something would expand, and how well it would penetrate.

As many here know, barrel length does have a huge impact on muzzle velocity, and muzzle velocity defines the post barrel projectile kinematics.

I had a group of kids as exchange students from Sweden one year.

I took them to the range and they all wanted to shoot the 500 S&W handgun.

The short barrel version had a very modest muzzle velocity compared to the H&R Handi-Rifle in the same caliber ... but the foot long flames from the powder that was still burning as the projectile exited the barrel made the short barrel revolver the handgun of choice. They wanted to shoot and take video of that gun ... every one of them.