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Through the looking glass: Gradient Lens Corp.'s affordable Hawkeye[C] borescope is a fascinating and useful tool -- but like Alice, your life may never be the same after you peer through this looking glass.

Looking down bores and chambers, into locking lug recesses, inside loading dies and brass cases, isn't for the faint-of-heart. You often discover things you wished you never knew about. But using a Hawkeye [C] borescope quickly becomes addictive. And using it when buying used guns or analyzing mechanical problems can save you the original cost of the borescope many times over. (Just imagine approaching a table at a gun show with a borescope tucked under your arm.)

Let me give you a few examples from my own experiences of using the Hawkeye borescope.

Is It A Bargain?

A pre-'64 Winchester Model 70 Featherweight in .243 Win recently hit my dealer's used gun rack. The metal and wood were in great shape, and looking down the 6mm bore with my naked eye, the rifling appeared to be clean and crisp. I happen to like both the caliber and the model, and I decided to make an offer. But before doing so, I asked for the opportunity to examine the bore with the Hawkeye. Glad I did. What appeared to be a decent bore turned out to be an eroded one from the throat to the muzzle. We're talking about that cracking, alligator skin-type condition that is often seen in the first few inches of the bore forward from the throat, but rarely all the way to the muzzle. The .243 was totally shot out. I passed on the piece and pity the fellow who ended up with it.

After cleaning another .243 -- a Ruger 77 with a pristine barrel -- I checked my work with the Hawkeye borescope. Looking down the barrel, everything looked clean until I hit the mid-point. There, for a distance of about 2 inches, were lumps of copper jacket material still adhering to the lands. I couldn't feel any constriction at that point with a patch or brush. With the naked eye, I certainly couldn't see the fouling. Yet, there it was, bathed in a brilliant copper light through the lens of the Hawkeye. A few passes with Sweets 7.62 solvent and it was gone.

Mystery Solved

I was puzzled by the lack of accuracy shown by a No. 1 Mk III Enfield that had been factory reconditioned at the Ishapore Armory in India. The piece looked absolutely brand new, yet it wouldn't group as well as an original 1918 BSA. Out came the borescope. Throat erosion from the spaghetti-like strands of cordite powder has to be seen to be believed. It takes the form of a many-pointed star or a series of little mountains and valleys in the throat area. Both Enfields exhibited throat erosion, but the barrel of the rebuilt rifle exhibited an erosion pattern extending from the throat to mid-bore whereas the erosion of the 1918 BSA bore was largely restricted to the throat itself. Puzzle solved. Without a borescope, I would still be assuming that the barrel of the rebuilt Enfield had to be in better overall condition than that of a 1918 antique.

I have a .308 Win across-the-course match rifle sporting a premium-grade stainless-steel match barrel. It's been a fantastically accurate target rifle and the current barrel has seen in the vicinity of 2,500 rounds down its tube, many in rapid-fire events. Borescopes make it possible to monitor bore wear, and I was curious. What I discovered with the Hawkeye was not a great deal of wear, but a very visible machining chatter mark about mid-bore. Given the quality of the barrel, it really did puzzle me. This might have well been one of those times when "ignorance is bliss." That chatter mark has not affected accuracy or accumulated fouling or had any other effect on the performance of the gun, yet psychologically, I now wish it weren't there.

And revolver barrel throats!!! Don't even look -- or you'll be picking up the phone and ordering a throat reamer kit from Brownells within the hour. The same goes for the reamer marks in modern revolver cylinders. I've even used the borescope to look for and locate burrs in the hammer slot of a frame.

In shotguns, the Hawkeye borescope really gives you a bird's eye view of how well you're doing in removing plastic and lead fouling from the chamber, forcing cone and choke. It also permits you to see how well any factory aftermarket choke tube mates with the interior surface of a bore and whether or not the tube is flush with its threaded seat when fully tightened. You can study the length and degree of finish of forcing cones and the design of fixed chokes.

When cleaning, the borescope permits you to objectively evaluate results as you test various chemicals, brushes, abrasives and cleaning protocols.

Did I say the use of a borescope is "addictive?" Once you own one, you'll be poking and probing into every firearm in your collection, discovering new uses every day as you do so.

Designed For Industry

The Hawkeye Precision Borescope is the creation of the Gradient Lens Corp., located in one of the optical capitals of the world, Rochester, N.Y. The Hawkeye Borescope is just one of a sophisticated family of optical examination instruments produced by the company that are used in industry to check the quality of everything from fuel injector nozzles to interior welds.

The Hawkeye borescope consists of three units: the borescope with attached eyepiece; a right angle mirror tube that slips over the borescope and rotates 360 degrees; and a Mini-Maglite light source that screws into a fitting at the eyepiece and serves as the handle. In use, the Mini-Maglite is screwed into the borescope; the right angle mirror tube is slipped over the borescope shaft; the light is turned on, and you're ready to take a look. The borescope can also be used without the rotating mirror tube, providing forward image viewing and is useful for examining the internal flashhole of a case, for example.

What is unique about the Hawkeye unit is the lens system. The makers have been able to eliminate the cost of grinding, polishing, coating and centering numerous micro-lenses normally associated with this type of instrument by substituting a series of short, optical glass rods or "gradient index lenses" that relay the optical image from the objective lens to the eyepiece lens. The resulting images are bright, color correct and very sharp. In fact, the depth-of-field of the Hawkeye extends from 1mm to infinity.

Gradient Lens Corp. offers two models of the Hawkeye.

There is the original model that features a fully adjustable focus with all the components packaged in a lockable custom metal carrying case. Normally selling for $760, Gradient is currently offering a $60 discount bringing the price down to $700.

The Big News

The real bargain is the new "Limited Edition" Hawkeye selling for $495. This model is exactly the same as the more expensive original except for the focus adjustment of the eyepiece, and the metal carrying case. In the original model, focus is adjusted by turning the eyepiece with nothing more than your fingers. In the "Limited Edition" borescope, the focus is factory set and I found it perfect for viewing; however, the eyepiece can readily be re-focused by loosening three small hex set screws and moving the eyepiece in or out. Frankly, given the extended field of view offered by the Hawkeye, the need for changing the focus should be minimal. For example, when viewing the large interior of a shotgun bore, I find that positioning the lens tube against one wall of the barrel provides a crisp image of the opposite wall.

The only other part of this optical system that is nice to have, but not essential, is the snap-on, right-angle eyepiece, which is offered as an accessory. When you're dealing with a bolt-action rifle with a high Monte Carlo stock, it's difficult to position your eye behind the eyepiece as the lens is fully inserted. The simple solution I found for most bolt-actions is to lay the rifle on its side when using the Hawkeye. The right-angle eyepiece sells for $275 and is offered for a reduced price of $195 if purchased with the more expensive model. If you're working primarily with modern stocked rifles, I would strongly recommend the purchase of this one accessory.

The borescope of the Slim model is 17 inches long and approximately .165 inch in diameter. The addition of the rotating mirror tube increases the probe diameter to .188 inch so it will work in any bore size from .22 through the shotgun gauges. In use, because of its 17-inch length, the lens tube is inserted from both the breech and the muzzle to view the entire barrel. Of course, in the case of most lever-action rifles and autoloaders, you're limited to viewing from the muzzle unless some degree of disassembly is possible. Autoloading and pump shotguns pose no problem since their barrels are easily detached.

For the professional gunsmith or barrel maker, Gradient Lens also offers Hawkeye compatible accessories such as video cameras and monitors, digital cameras, and high-intensity light sources.

The Hawkeye Borescope is a remarkable exploratory and diagnostic tool for the firearm owner. Its optical quality is superb, and its use is simple and straightforward. From a cost point of view, the Hawkeye is no more expensive than a quality pair of binoculars or a rifle scope; plus, it can save the owner many times its original cost when evaluating potential purchases over the years. And, yes, it's addictive.
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Author:Bodinson, Holt
Publication:Guns Magazine
Date:May 1, 2002
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