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Transparent AR-15 Lower? Spinel Might Make It Possible

A special ceramic called spinel {spin-ELL} that the U.S. Naval Research Laboratory (NRL) has been researching over the last 10 years could be used to make a variety of cool things: super-tough optics, glass-like armor, an almost-unbreakable smart phone case — maybe even a transparent lower for AR-15s or other gun parts.

“Spinel is actually a mineral, it’s magnesium aluminate,” says Dr. Jas Sanghera, who leads the research. “The advantage is it’s so much tougher, stronger, harder than glass. It provides better protection in more hostile environments—so it can withstand sand and rain erosion.”

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The U.S. Naval Research Laboratory uses a hot press to make spinel into conformable optics, like this flat sheet. “Ultimately, we’re going to hand it over to industry,” says Dr. Jas Sanghera, who leads the research, “so it has to be a scalable process.” Photo by U.S. Naval Research Laboratory/Jamie Hartman

Spinel can be mined as a gemstone; a famous example is the Black Prince’s Ruby, which is actually spinel with a color dopant. NRL chemists have also synthesized their own ultra-high purity spinel powder, and other synthetic versions are commercially available. “The precursors are all earth abundant, so it’s available in reasonably low cost,” says Sanghera.

“There are a lot of applications,” says Sanghera. He mentions watches and consumer electronics, like the smart phone, as examples. The military in particular may want to use spinel as transparent armor for vehicles and face shields.

A “bullet-proof” window today, for example, has layers of plastic and glass perhaps five inches thick. “If you replaced that with spinel, you’d reduce the weight by a factor of two or more,” says Sanghera. The military is also interested in using spinel to better protect visible and infrared cameras on planes and other platforms.

Glass doesn’t transmit infrared, so today’s optics are made of “exotic materials that are very soft and fragile,” and have multiple layers to compensate for color distortions. “So that’s what we’ve been doing now, developing new optical materials,” says Sanghera. Spinel windows could also protect sensors on space satellites, an area Sanghera’s interested in testing. NRL is also looking at spinel and other materials for next generation lasers.

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A technician cleans an infrared camera from the deck of the USS Cleveland (LPD 7). Spinel could one day replace the glass in military imaging systems, and the transparent material has potential use in firearms applications, such as receivers, pistol frames, optics, and magazines. Photo by U.S. Navy/Mass Communication Specialist 2nd Class Michael Russell

The U.S. Naval Research Laboratory is the Navy’s corporate laboratory, conducting scientific research and advanced technological development. The Laboratory, with nearly 2,800 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Mississippi and Monterey, California.

It’s not hard to imagine a number of potential uses for the transparent material in firearms applications: receivers, optics, magazines, to name just a few. What uses do you see for spinel? Let your imagination run wild in the comments section below.

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Comments (13)

    1. @ Bluehawk.

      I wouldn’t recommend it with the SPINEL (magnesium aluminate). If the Powder Charge is Significantly High in Temperature. Above 883.4F in a closed-off environment like a Barrel Firing Breech. The Magnesium in the Cartridge Casing could in theory Weld the Firing Breech Shut Permanently…

  1. Sorry to pee on everyone’s corn flakes, but who care? A transparent lower . . . what’s the advantage?

  2. Don’t know if I would want a clear gun. Cleaning the AR is already a project. Now every one could see what you missed! Clear mags like the ones for my 10-22 are a good idea.

  3. Ware does it stand on the hardness table? Might work as a penetrating projectile.Would probably stand up to hyper velocity. Use in in the rail gun in a magnetic sabot.–Use it on the leading edge of chopper blades for operating in heavy sand.–Make the domes for our future (or existing?) Mars and Moon bases. Tourist submarines. Or just another improved baking dish.

    1. @ OLD&GRUMPY.

      On the “Mohs” Scale.
      – Diamond rates a 10.
      – SPINEL (magnesium alumininate) or MgAl2O4, rates 7.5-8.0.
      – ALON (aluminum oxynitride) or AlON, rates 8.6.

  4. Not of the same material, but the transparent AR-15 Lower has been a reality for some time now as produced for public sale by the Tennessee Arms Company:

    Regardless, kudos to Woody for constructively finding a way to inject a gun related association in order to introduce us to such a cool mil-tech material.

  5. Hurricane windows! This would reduce the price and increase the safety effectiveness of these windows required in many locales in the Southeastern United States.

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