Anyone ever seen a bullet shot at memory foam?

[qajaq59]

After watching Myth Busters I guess the best mattress for stopping bullets would be a water bed.

 

[Damien45]

Actually, I would think there is a chance of stopping some rounds. A while back I took a stack of Phoenix Metro Phone Books, A-L listings, out in the desert for a shoot. Now that phone book was less then 10" thick (iirc). The results were:

Handguns:
9mm got about 3/4 through
.40 got about 2/3 through
.45 went completely through
.357 Mag, rewrote the book to A-B listings

Rifles:
.223 4/5th through
.308 went completely through
8mm Mauser completely through

So, I'd say it would be a lot of fun to test!

 

[Erebus]

After watching Myth Busters I guess the best mattress for stopping bullets would be a water bed.

They are hard to hold up in front of you though.

 

[karz10]

Any luck so far? I ordered a sample but haven't gotten it yet... I think one guy said he already had a sample, was wondering if he got a chance to shoot it yet....

Karz

 

[Lucky]

Same Here

HQ passed me on to the local distributors, but nothing yet.

I have gotten formulas though, that can be used to figure out the Thickness Efficiency (compared to armour steel).

QUOTE(Luckyorwhat @ Thu 5 Apr 2007 0448) *
Could you advise on how to determine thickness or mass efficiency?UNQUOTE

I have had good luck with particle board as a witness material. It is fairly regular in composition, and is soft enough that precise measurements can be made -- if your measurements are off by 2mm, say, and you measure 5mm penetration into steel, then your error is ~40%, but if you measure 250mm penetration into particle board, then your error is only ~1.5%.

Use a firearm and penetrator with a well-documented RHA penetration rating (say, 150gr FMJ 7.62mm NATO). Fire six shots, about a foot apart, into a ~2-foot thick stack of tightly-bound particle board oriented such that the boards are facing you (the penetrator strikes perpendicular to the face of the top board, and penetrates multiple boards). The exact depth will depend on the composition of the boards, your distance from them, bullet wobble imparted by your gun, and other things. Normalize this against the expected RHA penetration (4mm for 7.62mm FMJ, so if you penetrate 120mm your penetration ratio is 30.0). Eliminate the least-penetrating and most-penetrating samples, and average the rest. This will be your baseline penetration.

You should be able to obtain the density of your specimen materials (the foam) from matweb or the manufacturer. If not, though, then you need to measure the exact dimensions and weights of your specimens before shooting them to obtain their densities. In any case you need to measure their thickness so you can compute their thickness efficiencies later. Their densities will allow you to convert from thickness efficiency to mass efficiency.

Set up your particle boards again as before (fresh ones, but of the same composition, and preferably from the same batch) with six specimens glued to the outermost board, spaced one foot apart (measured center to center -- so if your specimens are eight inches wide, there will only be four inches between their edges). I like using a polyurethane (like Gorilla Glue) around the edges of the specimen only, so that the bullet doesn't have to penetrate any of the PU. Put a bullet through each specimen, as close to their centers as you can get. Measure the residual penetrations (from the outer face of the outermost board to the bottom of the craters -- do not measure from the outer face of the specimen!). Again, I like to eliminate the most- and least-penetration samples.

Use the difference between the baseline penetrations and residual penetrations to calculate the thickness efficiency of your specimens. If your baseline average penetration was 120mm, and your average residual penetration was 75mm, then the specimens were "worth" 45mm of particle board. Normalize this to eRHA by dividing 45mm by your penetration ratio (30.0 in the above example, which would give 1.5mm eRHA).

Divide this eRHA by the thickness of your specimens to get a thickness efficiency. If your specimens were 300mm thick, then your thickness efficiency would be 0.0050. To convert TE to ME, multiply TE by 7.86 (the density of RHA) and divide by the density of your specimen material. So if your foam had a density of 0.010, your ME would be 0.0050 * 7.86 / 0.010 = 3.9 (I'm not confident enough in my measurements, or in the consistency of my witness material, to quote more than two sigfigs).

Obviously if you have the money to spend you can use this same approach with a better rig .. HDPE instead of particle board, perhaps, and more than six sample shots (according to my statician friend, 200 samples are really needed for an ironclad claim, but six is good enough for my limited budget).

I'm an amateur, so take this all with a grain of salt. The process described was gleaned from reading IJIE articles, and practice.

Good luck!
-- TTK

 

[antipop]

This is why I love THR- nowhere else could I find the results of small arms fire on a mattress for science.

Ten e-awesome-dollars to the first one to make a suit out of it

 

[gezzer]

Personaly, I do not hide under the bed from threats.

Although, I use the water bed as an unloading barrel when I unload in any firearm in the house. .

 

[Roccobro]

Any update?

Justin

 

[SASS#23149]

Well son of a gun...

I was prowling our garage yesterday and found a very nice chunk of 'memory' foam,about 8" thick as I recall.It was a sample from a matress supplier when I was in that business.
..at the time could not think of any reason to keep it...almost tossed it..

but VOILA!!!! NOW I KNOW WHAT TO DO WITH IT.

It'll be a few days,but I'll see what 45 colt rounds at 800fps...and a few others of course,,,will do to it.

my .357 rounds will RFEALLY test it.!!

 

[Nomad101bc]

I am very tempted to shoot my tempurpedic pillow with my .40. Though I think standard hardball ammo will zip right through it with relative ease it might stop a hollow point.

 

[karz10]

Glad to see some other folks still interested. I'm still interested. I tried to get a sample of the material to use, but the sent me a small square an inch or so thick, not much help.

I'm not gonna shoot up my mattress, but maybe SASS can get us an update, that would be cool. Maybe someone else can get ahold of a piece or two also. If anyone knows where I can get a block as thick as mattress, I'd be happy to put a few rounds into it.

Karz