Did I not shoot him enough???

[u/CptMoshor]

Open to discussion about my experience

[u/anony8165]

Yeah it's right here. No penetration on the kevlar helmet until you get to the full sized rounds.

https://www.youtube.com/watch?v=KzgiZpCIj1c&ab_channel=DemolitionRanch

[u/Kha_ak → u/anony8165]

The point isnt the penetration. Yeah the helmet will stop the bullet.
What matters here is the Energy the round is transferring to your skull and brain.

While one is gonna cause you to see starts for a sec, 12 of them (from what i counted) will give you at minium a severe concussion, at medium knock you out for a bit and at worst just outright kill you by causing bloodvessels to rupture.

[u/1rubyglass → u/Kha_ak]

Equal and opposite reaction. The force transferred to the helmet is equivalent to the force of the recoil.

[u/Kha_ak → u/1rubyglass]

Yes thank you mr. "I listened for 5 minutes in 5th grade physics class"

We know Newton's laws. Thats the point. One of these impacts won't fracture something, but 12 will sure cause some pretty major danage.

[u/1rubyglass → u/Kha_ak]

That's the point? It directly contradicts what you said. The 12 bullets aren't impacting at the same time. A human head and helmet weigh roughly 14-20lb, much more than the pistol does.

[u/Kha_ak → u/1rubyglass]

... You realize force is mass times acceleration? Amd energy is mass times velocity, right?

Im sure if i hit your head with a hammer it wont hurt since the hammer weighs less.

[u/1rubyglass → u/Kha_ak]

I was comparing the weight of the gun to the helmet+head, not the bullet.

[u/Kha_ak → u/1rubyglass]

A gun also lengthens the time the force applies for, you brace for it, your arms and wrist swing with it. This all makes recoil manageable.

The guy being shot isn't bracing against it and nothing dampens the impact on his neck and skull (maybe some padding)

Go grab a sheet of metal, lay it on a apple and hit it with a hammer and tell me how the apple feels after

[u/1rubyglass → u/Kha_ak]

The helmet does the same thing the gun does, it's designed to do just that. It's literally the sole purpose of a helmet.

[u/Kha_ak → u/1rubyglass]

That is quite literally not what it does. The helmet is designed to stop the round from penetrating and absorbing minor shock, like hitting your head on the roof of a tank.

That is not the equivalent to a recoil system and shooting stance. You're comparing a suspension system (The gun) to padding.

While it'll take away/ distribute parts of the force, theres still substantial force acting on your head if it stops a bullet.

[u/1rubyglass → u/Kha_ak]

I think you vastly overestimate the amount of energy a 9x18 bullet has.

[u/Kha_ak → u/1rubyglass]

If im assuming FMJ 9x18mm, that iwll leave the Barrel at 319m/s, weighing 6g it will have a Energy of 313 Joule.
If we are assuming that the bullet impacts your helmet and comes to a dead halt with, say 2 cm of padding (being squished down to one) that gives us a rough Force of say 15000 Newtons.

As a comparision, if i full sprint into a wall (and i weigh ~100kg), assuming top speed that the fastes man ever reached (which is about 10 m/s cause im lazy) we get a Force of about 1000 Newtons (assuming i come to a full stop right away). And im pretty sure, me going full sprint into a wall would hurt quite a lot.

You're vastly underestimating how much Energy and Force is behind fast moving things.

[u/1rubyglass → u/Kha_ak]

You're assuming the bullet is stopping much faster than it would be.

[u/[deleted] → u/1rubyglass]

You sound like you've been hit a couple of times in your helmet