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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Fire Lapping a Barrel
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<blockquote data-quote="Bart B" data-source="post: 801706" data-attributes="member: 5302"><p>Yes, they use something like a lead or brass lap charged with abrasives to enlarge the tight spots in the very slightly undersize bore up to either their specs or those of the customer. They'll use a precision hole micrometer or air gauge to measure the diameters. When they've got a spread of less than .0001" and are at the desired specs, they do nothing else except mark the ends of the barrel blank where diameters start to flare out a bit. Those ends are cut off or reamed out by the 'smith fitting the barrel to the receiver. I think most high end barrel makers want the bore's finish to be between 10 and 15 microinch for best accuracy. Any smoother and steel tends to wipe off more bullet jacket material for some reason I don't fully understand.</p><p></p><p>Here's a good article on top-quality barrel making by one of the best:</p><p></p><p><a href="http://www.border-barrels.com/articles/bmart.htm" target="_blank">http://www.border-barrels.com/articles/bmart.htm</a></p><p></p><p>Note the section on "WHAT MAKES A BARREL ACCURATE"</p><p></p><p>Softer, non-embedding abrasives, such as JB, can easily "lap" out copper wash as well as power and primer hard fouling. But these do virtually no steel removing from the barrel itself.</p></blockquote><p></p>
[QUOTE="Bart B, post: 801706, member: 5302"] Yes, they use something like a lead or brass lap charged with abrasives to enlarge the tight spots in the very slightly undersize bore up to either their specs or those of the customer. They'll use a precision hole micrometer or air gauge to measure the diameters. When they've got a spread of less than .0001" and are at the desired specs, they do nothing else except mark the ends of the barrel blank where diameters start to flare out a bit. Those ends are cut off or reamed out by the 'smith fitting the barrel to the receiver. I think most high end barrel makers want the bore's finish to be between 10 and 15 microinch for best accuracy. Any smoother and steel tends to wipe off more bullet jacket material for some reason I don't fully understand. Here's a good article on top-quality barrel making by one of the best: [url]http://www.border-barrels.com/articles/bmart.htm[/url] Note the section on "WHAT MAKES A BARREL ACCURATE" Softer, non-embedding abrasives, such as JB, can easily "lap" out copper wash as well as power and primer hard fouling. But these do virtually no steel removing from the barrel itself. [/QUOTE]
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Fire Lapping a Barrel
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