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Polyurethane Might be the Key to Next-Gen Body Armor

by Ward Carroll on November 19, 2012

A cool new development in bullet stopping tech happening at Rice University.  This from the school’s web site:

A Rice University lab, in collaboration with researchers at the Massachusetts Institute of Technology and its Institute for Soldier Nanotechnologies, decided to find out by creating the nanoscale target materials, the microscale ammo and even the method for firing them.

Ned Thomas, dean of the George R. Brown School of Engineering at Rice and a materials scientist, holds a polyurethane disk with the bullets it stopped and sealed inside. Thomas is leading an investigation into the characteristics of such materials at the nanoscale.

In the process, they gathered a surprising amount of information about how materials called block copolymers dissipate the strain of sudden impact.

This video explains more:

Long time DT readers will remember the “Dragonskin” issue a couple of years ago.  This polymer tech could render that discussion moot and be a big game changer in the world of personal protection.

(Gouge: Mike Archer)

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{ 68 comments… read them below or add one }

nate November 19, 2012 at 11:00 am

So is this the same stuff one would use to coat and protect hardwood floors? If so, then could one just go down to the hardware store, buy a gallon or two, pour it in a frame, and make their own bullet proof glass?

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Jeff November 19, 2012 at 11:37 am

It'd probably be more involved than that. Layered applications of controlled thickness at varying specific temperature and humidity drying conditions.

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blight_ November 19, 2012 at 11:40 am

Probably not.

On the plus side, it might hold up better than bulletproof glass. I note that the example unit didn't shatter; but I have no idea what was fired into it.

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FormerDirtDart November 19, 2012 at 2:13 pm

They stated the sample was hit by 9mm slugs. One concern would be at what rate of speed does any penetration occur. If small particles can achieve shallow penetration at low velocity, the material might be worthless as bulletproof glass. Think of wind blown sand and grit becoming embedded in the material, slowly rendering the material opaque.. Not to mention how rapidly that might happen if the material was used on a vehicle, and even more so on unimproved roads and cross country.

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Thematerialsguy November 19, 2012 at 2:56 pm

You would shield it with an outer protective face.

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Thematerialsguy November 19, 2012 at 2:55 pm

Unlikely; they use the generalized "polyurethane", which is just a type of bonding which characterizes this polymer, the rest of the chemical composition (chemical backbones) are likely very different from your typical store bought urethane coating; which will yield very different material properties.

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Fil November 20, 2012 at 4:20 pm

Sure, just like how the carbon in your pencil and the carbon on your engagement band are the same thing. Right?

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tim November 20, 2012 at 6:43 pm

yeah, that's how it works.

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Steve November 21, 2012 at 10:50 am

Not the same stuff Nate. The polyurethane that this article is referring to would be a 2 component system, i.e. a (polymer and catalyst) or hardener if you prefer. Similar to you mixing an epoxy 2 component system together.
Typically for the properties they are looking for it would be a hot cure system. High end bowling balls are made of castable polyurethane. Currently some Jet planes are using a uniroyal polyurethane 2 component 85D hardness product that is in the same hardness range of bowling balls for their windshields. It keeps geese from landing on the pilots lap.
My guess is that for body armor its likely that the material (urethane) used would be a softer durometer than windshield material. Maybe not tho, I spose they could mold plates that connect together of harder material. It sure wouldn't be comfortable to have a rigid jacket to wear.
Its quite interesting. I produce custom polyurethane components for various industries & now I will have to play with several different scrap parts I have laying around and see if anything I have would work. Might be able to make myself some custom armor. Think I can purchase various weapons and do some R & D and write off the purchase's?? hmmm.

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tiger November 19, 2012 at 11:16 am

I think folks on this board will not be happy till they have Stormtrooper outfits from Star wars to wear. We need light saber resistant Armor!

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blight_ November 19, 2012 at 11:40 am

Hey, if we're rolling in 84 ton tanks… lul (see DoDbuzz)

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Nidi November 19, 2012 at 12:10 pm

Except Stormtrooper armor stopped neither lightsabers nor blasters. And as the Ewoks showed, they weren't particularly useful against blunt force trauma either. So I doubt they would be much good against bullets.

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Guest November 19, 2012 at 4:00 pm

Maybe not stormtroopers, but a US Colonial Marines set up wouldn't be too shabby in my eye :-P

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blight_ November 19, 2012 at 12:00 pm

Finally, something tech related.

Under rubber toughening, another wiki article:

"Many thermoplastics such as polystyrene and PMMA are brittle when stressed, a property which limits applications. A good way of strengthening such polymers is to copolymerise elastomeric chains during manufacture. The elastomer chains form separate phases in the solid, typically 10-20 micrometres in diameter, so that when the material is strained, crazes form at their surfaces, increasing the energy needed to break the material"

Might mitigate one of the weaknesses of boro-ceramics, which is that they are strong but brittle, and heavy. That said, what kind of weight, density and effective volume of material is required to stop an AK-47 round? Does the copolymer spall?

On the plus side, polymers can be molded and cast perhaps much more reliably and cheaply than ceramic plates. Curious where it'll go.

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Thematerialsguy November 19, 2012 at 3:20 pm

If your thinking about personal body armor; polyurethane alone will not supplant B4-C or Si-C. Look at how thick of a section of urethane they needed to stop just a 9mm bullet. You would be extremely bulky wearing that. In fact to my knowledge, there is no better way to currently stop a bullet in such a confined space then ceramics (since they erode the bullet, while crumbling=energy absorption). A support liner is used to support the ceramic-plate and catch any debris with forward momentum. These guys are actually trying to understand the fundamental mechanisms behind what makes polyurethane an effective energy absorber. And that piece they have in the photograph is mainly for show. This objective is far removed from any practical armor application. If you want to learn more about the challenges of developing ultra-light weight armor materials a good, albeit technical overview is found in "Progress in Ceramic Armor" published by the American Ceramic Society (http://www.wiley.com/WileyCDA/WileyTitle/productCd-1574981951,descCd-tableOfContents.html). And no, the co-polymer wouldn't spall because it's elongation to failure is too high/(it's not brittle); it would fail ductility first, I imagine.

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Daniel Thaler November 21, 2012 at 12:40 am

I'm sure your calculations are correct. Isn't it amazing that nanotechnology, at its beginnings, started with close examination of the lotus leaf.

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scott2311 March 24, 2013 at 12:48 pm

any thoughts on BAE systems liquid body armor ' shear thickening liquid ' ?

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TomUK November 19, 2012 at 12:10 pm

I think the keywords here may be 'nanoscale' and 'microscale ammo'. Interesting start, though.

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blight_ November 19, 2012 at 12:16 pm

There's always an issue with model systems, but the specific aim is a very standardized test system that can be eventually used to test all materials.

From: http://www.nanotech-now.com/news.cgi?story_id=462

Testing their ideas took special equipment. The research team came up with a miniaturized test method, dubbed the laser-induced projectile impact test (LIPIT), that uses a laser pulse to fire glass spheres about 3 microns in diameter. The spheres sit on one side of a thin absorbing film facing the target. When a pulse hits the film, the energy causes it to vaporize and the spheres to fly off, hitting speeds between .5 and 5 kilometers per second. Since the kinetic energy scales with velocity squared, the factor of 10 in speed translates to a factor of 100 in impact energy, Thomas said.

Lee calculated the impact in real-world terms: The spheres strike their target 2,000 times faster than an apple falling one meter hits the ground, but with a million times less force. However, because the sphere's impact area is so concentrated, the impact energy is more than 760 times greater. That leaves a mark, he said.

The team tested their materials in two ways: horizontally, with the impact perpendicular to the micro grain, and vertically, straight into the layered edges. They found the horizontal material best at stopping projectiles, perhaps because the layers reflect part of the incident shock wave. Beyond the melt zone in front of the projectile, the layers showed the ability to deform without breaking, which led to improved energy absorption.

"After the impact we can go in and cross-section the structure and see how deep the bullet got, and see what happened to these nice parallel layers," Thomas said. "They tell the story of the evolution of penetration of the projectile and help us understand what mechanisms, at the nanoscale, may be taking place in order for this to be such a great, high-performance, lightweight protection material."

Thomas would like to extend LIPIT testing to other lightweight, nanostructured materials like boron nitride, carbon nanotube-reinforced composites and graphite and graphene-based materials. The ultimate goal, he said, is to accelerate the design of metamaterials with precise control of their nano- and microstructures for a variety of applications.

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TomUK November 19, 2012 at 1:04 pm

I'm impressed. So how (and where) does all that kinetic energy dissipate overall ?

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Thematerialsguy November 19, 2012 at 3:27 pm

You can imagine a block-co-polymer with hard and soft segments as a series of springs and bars. The springs being the soft segments and the bars being the hard segments. Individually if you stress a bar, you might fracture it. If you stress a spring, it would send a shockwave down the spring. So imagine the KE of the bullet being transferred into billions (if not trillions) of these little springs and bars (being the polymer chains) causing movement/temperature rise on the molecular scale. The energy is being transformed into heat, utilized to in-elastically move the molecular branches, stored elastically in the bonds, or being transferred to the other interface and out of the system (in which case you could feel it/sense it)

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dee November 19, 2012 at 12:15 pm

Look at the 1 and 2 minute marks there is no advantage to be gained.

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Lance November 19, 2012 at 3:04 pm

Interesting for LE but doubt it can stop a 7.62x39mm bullet or a 5.45 or a 7.62x54R with out being VERY VERY THICK. Who knows but I doubt this will blow armor plates away tomorrow. more test need to be done and while interesting I do have doubts on it can stop rifle bullets.

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Guest November 19, 2012 at 3:58 pm

Whew! Good thing we have Lance here to set things straight. Those damn scientists just don't have a clue as to what they're talking about!

….idiot.

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Lance November 19, 2012 at 8:25 pm

Your a butt-head guest of I know your name on kit up pal. Just saying its a new technology and needs to see how it can work if at all against real weapons from a 9mm or .45 cal pistol. The thickness to stop a AK-47 round may be too thick to wear who knows I dont say this is crap im saying it needs more research before idiots in the army start buying them only to find out in combat it doesn't work as well.

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orly? November 20, 2012 at 12:19 am

Keep in mind the ECH is constructed from ballistic polyethylene, and IS able to defeat 7.62 rounds.
http://www.marinecorpstimes.com/news/2011/03/mari

The ECH is NOT that much thicker than an ACH. It IS possible for this NEW Polyurethane to do the same.

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blight_ November 20, 2012 at 9:00 am

From http://www.ballisticsupplies.com/soft_armor.html

"Ballistic resistant polyethylene armor is manufactured from woven ECPE (extended chain polyethylene) diverse [Ed: obviously typo, but "diverse"? Fibers? From figures, it looks like sheets of fiber stacked in 90-degree rotated layers] that are injected with either epoxy's, silicones, urethanes, vinylesters, are polyethylene resins, then placed in a hydraulic hot press to form flat rigid sheets of opaque ballistic resistant armor."

Edit: Above is taken from http://www.pinnaclearmor.com/transport-armor/armo

"Ballistic resistant polyethylene armor is manufactured from woven ECPE (extended chain polyethylene) fibers that are injected with either epoxies, silicones, urethanes, vinylesters or polyethylene resins, then placed in a hydraulic hot press or autoclave to form flat rigid sheets of opaque ballistic resistant armor. End use applications dictate type of injection and method of manufacture."

tmb2 November 21, 2012 at 1:46 am

Lance, nobody is suggesting the Army is going to stick this in a vest tomorrow, next year, or in 5 years.

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zak November 20, 2012 at 11:17 am

it's research, not even a prototype. If we never did any research unless it gave us exactly what we're looking for today we'd never do research and in turn we'd never make advances.

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Dillard November 19, 2012 at 5:23 pm

ITS A START FOR PETES SAKE….

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scott November 1, 2013 at 10:00 am

hey its better than nothing

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Gustavo November 19, 2012 at 5:24 pm

What about performance under heat?…

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thematerialsguy November 19, 2012 at 11:35 pm

That's actually a great question. Since they claim they are using a block-copolymer of hard and soft segments; that means that the hard segments are below their glass transition temperature, and the soft segments are above it. So depending on these transitions, the mechanical properties drop off may be too significant at elevated temperatures and is definitely a concern.

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Joe November 20, 2012 at 8:51 am

I know how your mom performs when under heat…

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Conradswims November 19, 2012 at 6:29 pm

Body armor that floats! That should be the goal.

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orly? November 19, 2012 at 7:27 pm

Tbh, Dyneema is buoyant.

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orly? November 19, 2012 at 7:33 pm

If the Enhanced Combat Helmet is any indication of progress, I am curious on what else could be made.

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Chris November 27, 2012 at 10:45 am

Hey speedy, what do you know about ECH???

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Speedy November 19, 2012 at 8:18 pm

Would they layer it with Kevlar and other stuff, make it lighter then current armour.

I do wonder if the guy in the photo was holding the disc when it was shot at… that would have been cool to see.

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stephen russell November 19, 2012 at 8:54 pm

Saw this in the TV show pilot Knight Rider 2008, bullets would hit car & body would absorb bullets like this MIT armor gel.
Must for DoD & Security alone.
Cut down on weight??

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Larry November 20, 2012 at 5:47 pm

Come on people, referencing a TV show? Let's get back to reality or are you also preparing for the 'zombie-pocalypse'?

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anthony November 20, 2012 at 6:00 am

I am glad to hear that our company helped to get this safety "polymers"on the market for safety purposes also..

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fredhandy November 20, 2012 at 8:46 am

ok good ideer but how about using a ak round our a 45/7.62 round?

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Lee November 20, 2012 at 11:36 am

It sounds like it is a hell of a lot better than the armor we had in Nam, where a bullet went in one side and came out of the other to go into your body.

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Major Hassle November 21, 2012 at 10:16 pm

that's why they made great seat cushions in helo's… the round that came through the helo belly, you at least could save your butt….

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Josh November 20, 2012 at 3:41 pm

This tech combined with an underlying layer of a rheostatic fluid could be a very effective body armor capable of protecting places that are basically impossible to protect now – like the armpit area for example.

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Josh November 20, 2012 at 3:44 pm

A magnetorheological fluid could also be applicable. Interesting stuff.

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Scott November 20, 2012 at 5:59 pm

To Ward Carroll,__Call Leslie Duke at ballisticsreasearch.com. He's already manufacturing a polymer based armor he developed. I don't know how similar it is to the polyurethane technology, but I know it works incredibly well at bullet stopping and capturing. I believe it's already in use in the field.

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bobbymike November 20, 2012 at 11:29 pm

We should insure large R&D dollars for materials research. It is incredible what the nano future will hold. That includes energetic materials as well for propulsion and advanced explosives.

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echo charlie November 21, 2012 at 12:42 am

So, he said something to the effect that the polyurethane target performed better at stopping the slugs than an equivalent steel target while weighing less than a seventh as much…
Huh?! That polyurethane chunk looks to be about two inches thick… Anyone doubt a steel chunk a seventh of that thickness would stop the 9mm slugs with zero penetration?

If polyurethane is a little denser than water as I recall, his factor of seven comment seems to imply an equivalent thickness of steel target is being discussed. Two inches of steel for small arms armor is a lot of steel armor.

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Steve November 21, 2012 at 11:23 am

My guess is the chunk of urethane he's holding weighs in at less than a pound, probably around 300grams. Ive shot FMJ rounds of 7.62 x 36 SKS through a 1/4" steel plate. It almost kindo didnt go through, it punched a hole through the plate and the projectile (deformed it was) was inches from the hole it punched through.
So if the urethane he's holding was 300 grams the equivalent weight for steel would be 2100 grams or 4.6 pounds (at his 7:1 ratio he's claiming). The sample he's holding looks to be around 4.5 inches in diameter, so for a steel equivalent of 4.6 pounds the disc would have to be slightly over 1.0 inch thick to achieve that weight. At that thickness my bet is it'd stop anything short of a grenade launcher.
FWIW I mix castable urethane systems daily, so my guess on the weight of his sample is based on working experience.

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Doug November 22, 2012 at 2:08 am

It was a thick sample of polyurethane, but the projectiles were intercepted at the topmost layers.

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john November 26, 2012 at 12:54 am

3/8ths AR500 steel stops a .308 with a tiny dent as the impact point. It'd take approx. 40 said rounds in a 7 inch circle to penetrate 3/16th AR 500 ( high hardened steel) AR means abrasive resistant and used as bull dozer blades etc. and armor.
The totally vague, teckno BS used by the self styled author, tells little of what we need to know; such as wt. per S2 and thickness to defeat a 7.62mm x.39mm AK round.
. Dyneema and Spectra shield are polymers and been around for 15 yrs. They need a strike plate to stop these rounds, after pressed into plates and they do float and also BURN.

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blight_ November 26, 2012 at 9:53 am

I'm pretty sure the original intent of the authors, per the Nature Communications, is more about the model system used to test ballistic properties and the material sciences aspect of figuring out *why* things work the way they do.

The investigator is a polymers guy, and by changing polymer composition can test a variety of materials properties relatively quickly. I suspect he will use the technique for other materials, if he hasn't already.

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WALT VANCURA November 21, 2012 at 11:28 am

AS LONG AS IT SAVES MORE LIVES !!!!

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scott November 1, 2013 at 10:03 am

i fucking absolutely hope so

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anonyomous November 21, 2012 at 1:28 pm

have you read the book "SYNERGY"?

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ANONYMOUS November 21, 2012 at 1:30 pm

SYNEREGY

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Ed November 24, 2012 at 5:38 pm

Best way to Stop a Bullet is to stop making guns the fire them. Then dont sell guns. Im kidding. really.

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blight_ November 26, 2012 at 9:54 am

Yeah, until someone makes a zip gun. Are you going to ban pipes and nails? Or when they melt a lead ball and make their own saltpeter at home?

You can't ban criminal.

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scott November 1, 2013 at 10:06 am

you can also make one with a 3-d printer. it will just take a while to print because it print one layer a time so don't make it too thick otherwise it will take forever to print

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ashurbanipal December 4, 2012 at 1:18 am

I’d settle for the Master Chief’s armor. (from Halo)

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cards games March 15, 2013 at 5:56 pm
scott November 1, 2013 at 10:07 am

what does this have to do with the polyurethane body armor

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blight_ November 19, 2012 at 4:52 pm

I've heard some pluses and minuses regarding those SLA Marshall studies post WW2…

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blight_ November 26, 2012 at 11:27 am

We're a long way from the Spartans of Halo, the T-11B of Fallout…and how does jumping from buildings and stabbing people in the throat stay relevant in the modern battlefield again?

The real Assassins were exterminated by the Mongols for a reason: individual skill rarely triumphs against organized militaries.

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gonger November 27, 2012 at 1:56 am

I'd settle for half of the stuff you get in Ghost Recon: Future Soldier.

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scott November 1, 2013 at 10:01 am

i would have loved to see that happen

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