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October 22nd, 2016

Borescope Basics — How to Diagnose Problems in Your Barrels

Hawkeye borescope POV lens

Hawkeye borescope POV lensA quality borescope is a pricey tool, but once you get to use one, it’s hard to imagine how you ever did without it. To learn how a borescope can help you diagnose barrel issues, you should read a Rifle Shooter magazine feature story, What the Eye Can See.

In this article, writer Terry Wieland explains how to inspect for defects in new barrels, how to recognize different kinds of fouling (in both barrels and brass), and how to spot throat erosion in its early stages. Terry uses a Gradient Lens HawkEye BoreScope. The current generation of HawkEyes can be attached to a still or video camera to record digital images of your bore. The most interesting part of the article is on the second page. There, author Wieland provides photos of various types of internal flaws that can appear in barrels. This will help you spot pitting, excessive land wear, rust damage, and damage from corrosive primers.

Wieland notes that BoreScopes aren’t just for barrels: “The borescope has other uses as well. It can be used to examine the interior of a cartridge case to look for the beginnings of a case separation or to examine the interior of a loading die that is giving you trouble. When you consider the number of tubular objects that play such an important role in rifle shooting, it is a wonder we were ever able to function without such a method of studying bores.”

This Gradient Lens video shows how to correctly borescope your barrel:

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January 2nd, 2008

Barrel Throat Erosion — Reality Revealed

So what does a “worn-out” barrel really look like? Tom Myers answered that question when he removed a 6.5-284 barrel and cut it down the middle to reveal throat wear. As you can see, there is a gap of about 5mm before the lands begin and you can see how the lands have thinned at the ends. (Note: even in a new barrel, there would be a section of freebore, so not all the 5mm gap represents wear.) There is actually just about 2mm of lands worn away. Tom notes: “Since I started out, I’ve chased the lands, moving out the seating depth .086″ (2.18 mm). I always seat to touch. My final touch dimension was 2.440″ with a Stoney Point .26 cal collet.”

Except for the 2mm of wear, the rifling otherwise looks decent, suggesting that setting back and rechambering this barrel could extend its useful life. Tom reports: “This was something I just thought I’d share if anyone was interested. I recently had to re-barrel my favorite prone rifle after its scores at 1,000 started to slip. I only ever shot Sierra 142gr MatchKings with VV N165 out of this barrel. It is a Hart and of course is button-rifled. I documented every round through the gun and got 2,300 over 4 years. Since I have the facilities, I used wire EDM (Electro Discharge Machining) to section the shot-out barrel in half. It was in amazingly good shape upon close inspection.”

Tom could have had this barrel set back, but he observed, “Lately I have had to increase powder charge to maintain 2,950 fps muzzle velocity. So to set it back would have only increased that problem. [And] I had a brand new 30″ Krieger all ready to screw on. I figured it was unlikely I’d get another full season on the old barrel, so I took it off.”

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