A customer filleted his eyebrow with the ocular of a night vision riflescope— courtesy of the recoil of 12-gauge, 3-inch buckshot shot through a Remington 870 pump shotgun. He demanded to know how the scope could have specifications that state it had been tested with recoil up to a .50 BMG.
The product may well have passed recoil tests up to the g-forces generated by the big, .50 cartridge (which, in general, is quite reasonable), but that figure would depend on the recoil characteristics out of that specific size and weight gun.
However, more importantly, eye relief specifications for an optic have nothing to do with recoil ratings or the suitability of you using them on a certain platform. Whether or not an optic is suitable to mount on a particular rifle has to do with how that exact platform will recoil, along with your ability to prevent scope-eye injury due to short eye relief.
Most night vison electro-optics require eye relief of 1 to 3 inches. So, be aware of the minimum distance of eye relief you require when shooting that gun and load before you attempt to fire with such a device.
Keep in mind that the cartridge is not the deciding factor regarding the adequacy of use of an electro-optic on a gun; it’s the gun itself. It’s mostly the size and weight of the gun that mitigate recoil, as well as other attributes, such as muzzle devices and your ability to control that firearm.
For instance, the muzzle brake on my Weatherby Vanguard in .300 Winchester is so efficient (once you ignore the obnoxious concussion), that it has much less recoil energy than my lightweight Howa 1500 in .30-06. An experienced shooter with a .458 SOCOM AR might well be able to use a night vision electro-optic with a 2.5-inch eye relief due to training and familiarity.
Knowing how to use a firm support hand or vertical fore grip, in addition to opposing force, helps. An unseasoned shooter with an electro-optic scope on a .308 bolt gun and a light hold could open up his forehead. Ultimately, the burden still falls on the end user to make the best decision regarding the safety and appropriateness of the use of an electro-optic riflescope on their rifle.
“Keep in mind that the cartridge is not the deciding factor regarding the adequacy of use of an electro-optic on a gun; it’s the gun itself.”
Recoil Ratings With Electro-optics And Specification Determination
I asked contacts working for half a dozen of the most popular current purveyors of night vision equipment exactly how they determine recoil ratings. As expected, I got half a dozen answers.
U.S. Night Vision and Trijicon were very forthcoming and specific. They have to be, because they supply military and LE around the world. U.S. Night Vision is an authorized DoD repair/ refurbishment depot, and it provides world-class service to “good guys.” Manufacturers with imported products are generally a bit more ambiguous in their recoil rating claims—or choose not to address this specification at all.
To clarify, this article defines “electro-optics night vision riflescopes” as those using image-intensified tubes (IIT) or infrared thermal units.
The standard-issue PVS-14 night vision monocular is rated to withstand the recoil of a 5.56 cartridge. That rating to 5.56 is when it’s fired from an issue M-4 carbine. Most failures of the PVS-14 can be traced to full-auto platforms of any caliber or with cartridges exceeding the 5.56 in a gun otherwise similar to the M4.
There are two main IIT manufacturers: ITT and L3. Steve Gibbons from U.S. Night Vision said that ITT has always advised that it produces two types of image tubes—weapon grade and nonweapon grade. L3 would state that it made only one grade and that it was suitable for both weapon and other applications.
Trijicon tests products to the requirements of MIL-STD-810G (readers, after you’re done hopefully enjoying this article, go online and Google “MIL-STD-810”). A tiny part of Trijicon’s brutal overall testing of the products is using it on its shock machine, tuned to replicate 5,000 rounds through an issue M4 and 1,000 rounds from an issue MK13 Mod 5 SOCOM in 7.62. The MK 13 is a Remington 700-based chassis rifle in .300 Winchester Magnum.
“Knowing how to use a firm support hand or vertical fore grip, in addition to opposing force, helps.”
Some companies use accelerometers in addition to actual firearms to duplicate recoil. Jeff Murray with Sellmark (Pulsar) states the company works with a local university and their Ph.D. mechanical engineering students to test and verify the recoil energy of several firearms using accelerometers. They then develop a cross-reference chart from that data for other calibers so they can similarly test products on a recoil machine.
Another popular company installs and shoots with electro-optics mounted on various guns with increasingly large cartridges and recoil energy/velocity until the products break. Then, they back down.
Circuitry is often the culprit in thermal device failure, whereas in IIT optics, it is twofold and can often be related to the delamination of image tubes or housing and battery compartment components.
So, remember: When determining if a specific electro-optic riflescope is suitable for your application, do so at your own peril— or risk scope-eye.
How do I know? The name of this column isn’t “Scope-Eye Chronicles” for nothing!
L3 (Insight Technology, Inc.)
U.S. Night Vision Corp.
Steven K. Ledin is a former U.S. Navy nuclear gunner’s mate and current director of a prominent online optics retailer. He’s a CCW and NRA instructor and has been a sponsored competitive shooter and private investigator. He has hunted (and gotten lost) from Alaska to Africa.
Editor’s Note: A version of this article first appeared in the November 2017 print issue of Gun World Magazine.