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Comment by SEJeff | Hacker News Reader

This is exactly how a Soviet style RPG works. Ironically, it is also why the "bird cage armor" works so well against the RPG. Here is a picture of a Stryker combat vehicle from when I was in Mosul Iraq circa 2004ish:

http://www.digitalprognosis.com/album/images/iraqpics/the-st...

The slats are smaller than the height of the outer explosive and prematurely detonate it. As a result, the penetrator simply bounces off the armor harmlessly.

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I thought the slats were to provide stand off distance for explosively formed projectiles.

If the explosively formed jet forms more than a few inches from the armor, it's way less effective.

The Vampir uses a tandem charge -- Two successive charges. The point of this is to counter reactive armor, which is designed to counter explosively formed projectiles.

The "cage" slats can be effective against both.

That's backwards. Explosively formed jets need space to form, so work better if they detonate a little distance from the target.

No, you're right. Explosively formed projectiles work best when formed a few inches from the armor. However, they have a sweet spot and if the distance is too far, they don't work. I figured that's what the cages were for.

Nope, we had them in Iraq before EFPs were really a thing (Thanks Iranain Quds Force for that). They were specifically for RPGs, which was one of the few things that could take out a Stryker without it. They even tried those Soviet parachute anti-tank grenades, but the Stryker is much faster than a tank and just moved away in time. That being said, the I'm sure this slat (birdcage as we called it) armor would help with that as well.

I thought an RPG _was_ an EFP? The round is just a shaped charge with a copper liner that penetrates the armour. So the slatted armour stops both RPGs and EFP-based IEDs.

The usual RPG with a HEAT shaped charge doesn't destroy by forging a penetrator that then potentially travels some distance to the target, it produces an intense, narrow jet that'll cut through a lot of material.

Not really. EFPs (in Iraq) were more or less IEDv2 in that they were simply much more lethal than the original IEDs:

http://www.cbsnews.com/news/us-sees-new-weapon-in-iraq-irani...

I though slat armour worked because RPGs only had a detonator in the nose, so unless you were very unlucky and the tip of the RPG hit a slat, the RPG would just jam itself between two of the slats.

Then they make the new guy get them out with a pry bar.

I saw that a few times actually, but only when the idiot firing the thing didn't pull the safety pin out of the warhead. The RPG is surprisingly safe when you neglect to remove the safety and will happily fire, but not explode in that circumstance. It was around the height of the Fallujah offensive we saw that happen.

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