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GUNS Magazine Digital May 2011 - Page 36
John Barsness he one part of guns we really can’t examine closely is the inside of the barrel. The rest of a rifle, shotgun or handgun can be disassembled and examined closely, but we really can’t see the details of a 24" rifle bore—unless we use a bore scope. T The late Dave Gentry, a well-known custom gunsmith from Montana, introduced me to the virtues of a bore scope almost 20-years ago. A major firearms company had loaned me a .300 Winchester Magnum for evaluation and a possible magazine write-up. This company was (and is) well known for the accuracy of its rifles, and the .300 Winchester is considered an accurate round, so it was disheartening to look downrange and see 30-caliber holes scattered across 2" or 3" of paper. The scope was a proven Bausch and Lomb. The action screws were Even if you allow one rifle to cool while shooting another, eventually the throat will erode enough to affect accuracy. A bore scope can provide an early warning. tight, and a folded piece of paper slid easily between the fore-end and the free-floated barrel. The bore looked nice and shiny when held toward the overhead light in my shop, but still the rifle refused to shoot accurately with either handloads or factory ammunition. Finally I called Dave, since during his career he’d encountered about every rifle problem in the known universe. He said it sounded like I’d done all the sensible stuff, but if I wanted to bring the rifle into his shop he’d look it over. Dave only spent a couple of minutes examining the outside of the rifle before putting it in a padded vise on his bench. Then he assembled his bore scope and carefully inserted it into the barrel. Bending over slightly, he squinted into the eyepiece of the scope as he slowly eased its thin tube back and forth. Finally he stepped back and said, “I think I found your problem. Take a look.” I bent and peered into the scope, seeing only some mysterious shadows. “What am I supposed to be looking for?” “Slide It Back And Forth A Little.” With the scope moving, the rifling immediately became apparent. The angle of the lands and grooves could even be seen, including some toolmarks—that is, except for a 1/4" of the bore, where the rifling was missing. I stood up and looked at Dave, somewhat startled. “There’s a gap in the rifling.” Dave laughed. “I bet that has something to do with your problems.” He guessed that a big chip of steel had somehow gouged out a ring inside the bore during the reaming process. Since Dave spent part of his early training in the shop of a well-known barrel maker, he was probably right. Even more interesting than the rifling gap, was the fact that it couldn’t 36 WWW.GUNSMAGAZINE.COM • MAY 2011