H&K MP7A1 versus Ballistic Helmet [High-Tech]

[Ragitsu]

http://www.youtube.com/watch?v=rMj73QKr7oI

This is probably heavily slanted in H&K's favor, but will the 4.6mm round fired by the H&K MP7A1 out of High-Tech defeat the helmet DR of the modern day ballisic helmet also out of High-Tech?

[nick012000]

Originally Posted by Ragitsu

http://www.youtube.com/watch?v=rMj73QKr7oI

This is probably heavily slanted in H&K's favor, but will the 4.6mm round fired by the H&K MP7A1 out of High-Tech defeat the helmet DR of the modern day ballisic helmet also out of High-Tech?

Yes. Helmet has 12 DR, and the gun does an average of 15 damage before damage multipliers are taken into account.

[DouglasCole]

Originally Posted by Ragitsu

http://www.youtube.com/watch?v=rMj73QKr7oI

This is probably heavily slanted in H&K's favor, but will the 4.6mm round fired by the H&K MP7A1 out of High-Tech defeat the helmet DR of the modern day ballisic helmet also out of High-Tech?

Yes. This was probably the design decision in choosing the damage. Using my own formulas, the MP7 shot only ekes out 9.7pts of penetration. That's just not enough to punch through the DR12 of the helmet, but a semi-armor piercing round (no longer an option in 4e) would make that DR12 into DR9.6, making the MP7 barely capable of penetrating the helmet. High Tech gives the MP7 and P90 bullets a LOT of credit.

Edit:

More explicit: out of the MP7 my formula puts the 4.6x33mm round at 2d+2(1.25 to 1.5)[0.5]. The 5.7x28mm from the P90 is 2d+3(1.25 to 1.5)[0.5]

GURPS 4e takes this as 4d+1 pi- and 3d-1(2) pi-. I mildly object to these low energy rounds doing (esp for the P90) more penetration than a .223 at point blank range (equiv of 6d-2, or 5d+1.5 for the 5.7x28mm; 5d or 5d+1 for the .223 with more than 3x the energy and higher bullet mass).

The bullet construction on the SS190 round for the 5.7 is pretty good, though, probably justifying either the 1.25 (for 12.5pts average penetration, just cable of defeating the DR12 helmet) or the 1.5 (15pts penetration, decisively penetrating the helmet). But the energy of the rounds and small mass and cross section probably don't wound well. Even if you assume the bullet fragments, my (ad hoc) calculations only give a wound channel modifier of 0.7 rather than 0.2 or 0.3 if it goes right through or 0.5 if it yaws to 90deg as it's designed. So we're probably talking pi- no matter WHAT system you use; the only question if if the raw penetrations and damage numbers are quite as high as stated. The 4d+1 pi- is pretty playable (I'd apply half damage to all targets, though, at least); the 3d-1(2) a bit less so.

[nick012000]

Of course, even now, it'll only do like 1 point of damage to the guy wearing it. Well, unless it's a Called Shot to the skull, anyway. Then you'll do 4.

Then again, neither of us was taking into account the ammo upgrades, either; you could do 8d-1 damage with a hot-loaded APFSDSDU bullet, with an armor penetration of (2) and no damage step decrease, since it's already Small Piercing. ;)

[Ragitsu]

Does the DR 12 just account for one "side" of the helmet, or anything that tries to pass through one side and out the other? If not, then it would effectively be DR 12 + 12 the bullet needs to pass through.

Originally Posted by nick012000

Of course, even now, it'll only do like 1 point of damage to the guy wearing it. Well, unless it's a Called Shot to the skull, anyway. Then you'll do 4.

Does this factor in the skull DR of the target?

[SuedodeuS]

Originally Posted by Ragitsu

Does the DR 12 just account for one "side" of the helmet, or anything that tries to pass through one side and out the other? If not, then it would effectively be DR 12 + 12 the bullet needs to pass through.

Indeed. For the round to get through both sides of the helmet, it would have to do 24+ damage. That's basically max damage. Of course, he is essentially hitting the helmet dead center, so maximum damage might be correct here.

That, or the helmet depicted isn't DR 12. Or the weapon is actually using AP ammo.

[Ragitsu]

Originally Posted by SuedodeuS

That, or the helmet depicted isn't DR 12. Or the weapon is actually using AP ammo.

Or perhaps even both of these factors, in which case the demonstration really is rigged in the MP7's favor.

[jacobmuller]

The basic ammo as listed will penetrate the helmet as listed.

But it would need armour piercing ammunition to match the video result.
And a good damage roll to achieve overpentration v's a head B408: APHC 4d+1(2) v's DR12+DR2+HP10+DR12...

The 5.56s listed have better penetration and range. Wasn't there a pistol made to fire them?

[Ragitsu]

Originally Posted by jacobmuller

The 5.56s listed have better penetration and range. Wasn't there a pistol made to fire them?

Average damage (3s on all d of a 5d caliber) is 15 for the 5.56mm, right?

As for the pistol: http://www.gunblast.com/Bushmaster-Pistol.htm

[Anthony]

First of all, GURPS has issues with armor layering. Secondly, the video shows multiple hits on the helmet in a single spot. Real armor is somewhat ablative, so by the second or third shot the front layer isn't offering much protection.