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Comment by intpx | Hacker News Reader

my back of the napkin math only puts this around the same stopping power as plywood of similar thickness. Sand bags work a lot better and are a hell of a lot easier and cheaper to produce

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A 45cm thickness of plywood would be an enormous amount of plywood, unless you're only covering a very small area.

What I am talking about is a concrete based foam, with small fiber reinforcement. Basically a bullet catch, that uses space to slow things down, rather than the harder job of stopping it outright. The 45cm number is if one uses a very low density mixture, since it’d be best used when space isn’t a concern. So it’s actually somewhat comparable to styrofoam, but doesn’t burn. That said, there is a wide range of potential mixtures, ranging anywhere from straight concrete to pure foam, so one can increase the density, and make it more compact, but it’s about what you are optimizing for. So that yes the actual capabilities of whatever is being referenced will be a bit confusing unless density is explicitly mentioned. A big prefabricated slab of what I am considering is human movable, and everything needed for on site application fits in a pickup truck. Not quite suitable for frontline application, but would be a great option for those in defensive positions farther back.

Something as simple a spraying a few to several inches some over a tarp would offer huge overhead protection from things like drone grenades or suicide drones in a trench, were implementing wood and sandbags isn’t as widely viable as just dropping a slab that supports it’s own weight.

Plywood rots unless protected. But if you're going for engineered solutions then plywood layers spaced apart with something a bit more flexible/compressible would be more effective and possibly lighter than a solid block of wood.

https://shocklayer.com/blogs/news/bulletproof-material-under...

From my experience shooting plywood, the 9mm would have no problem going through the same thickness. He is legitimately on to something with his process.

What are you on about. 45cm is INCREDIBLY thick, and a solid plywood block of that thickness will probably stop high caliber rifle bullets.

I've used telephone books as backstops in the past and abour 3-4 of them is enough to stop a handgun bullet easily.

We use 10mm mild steel plates for targets, and they don't even dent when shot with a 9mm round.

What are anybody in this thread on about with 45 centimeters? He stopped a 9mm with about four cenitmeters. Skip to 53:00

You are literally replying to a comment thread where OP said [about plywood] "While not suitable as personal armor due to thickness (generally around 1.5ft/45cm)"

Did you skip that entire part of the conversation and just went to the final comment in the tree?

Spacebacon said:

> From my experience shooting plywood, the 9mm would have no problem going through the same thickness. He is legitimately on to something with his process.

He's obviously talking about nilered's result. I have no idea what you people are on about with 45cm, 45cm of anything besides styrofoam will stop a bullet.

I have no idea how you read this comment thread and conclude that obviously he's talking about nilred's result and not the comments he was replying to. It's not obvious at all, in fact I don't know how you arrived at this conclusion.

I have no idea how you could read spacebacon's comment and conclude that he believes damn near half a meter of plywood would be insufficient to stop a 9mm bullet. That's so absurd it should have stopped you in your tracks and had you reevaluate what it was spacebacon was saying. How can you seriously believe he was claiming to have experience shooting at half a meter of plywood? The very premise is absurd.

Either spacebacon is completely insane, or he was talking about nilered's video. You chose the 'he's insane' interpretation. I say you're obviously wrong.

When you say "his process", you're talking about nilered's process right?

A 9mm would get through 45 centimetres of plywood???

Nilered didn't use 45 centimeters of densified wood, he used maybe four centimeters of it.

Would a wet sandbag have more stopping power than a dry one? Or does that reduce the sheering strength?

Water is very effective at stopping bullets, so I would assume so.

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