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Rifles, Reloading, Optics, Equipment
Gunsmithing
Why dial a rifle bore within .0001"
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<blockquote data-quote="Clark" data-source="post: 1159719" data-attributes="member: 6600"><p>In Oct 2010 I had a new PM1236 lathe and wanted to put 7mm Loather Walther barrel on a 7x57 VZ24.</p><p></p><p></p><p>But first I would practice by put a take off 7mmRM Rem700 barrel on a 1908 Braz Mauser.</p><p>I dialed in with the Intrepid to 0.0001"</p><p>I cut off the Rem threads with a parting tool, but did not deburr the hole.</p><p>The 7mmRemMag reamer got off center with the burr and visibly wobbled off center until it headspaced.</p><p>I measured the chamber and it was 0.0050".</p><p>I took it to the range and shot it anyway, along with the other rifles I did.</p><p>The rifle shoots better than I can.</p><p></p><p>I thought concentricity was important.</p><p>That math and testing by A.A. Abbato had to do with ammo concentricity.</p><p><a href="http://www.thehighroad.org/archive/index.php/t-617604.html" target="_blank">Concentricity - How much more accurate? - THR</a></p><p></p><p>It turns out that run out in ammo is rotationally randomly inserted, while run out in chamber is consistent, and throws bullets off center in the same direction into the same small group.</p><p></p><p>It sometimes angers gunsmiths when I point this out.</p><p>They wasted their whole lives dialing in barrels.</p><p></p><p>But it is a one time cost, no harm no foul.</p></blockquote><p></p>
[QUOTE="Clark, post: 1159719, member: 6600"] In Oct 2010 I had a new PM1236 lathe and wanted to put 7mm Loather Walther barrel on a 7x57 VZ24. But first I would practice by put a take off 7mmRM Rem700 barrel on a 1908 Braz Mauser. I dialed in with the Intrepid to 0.0001" I cut off the Rem threads with a parting tool, but did not deburr the hole. The 7mmRemMag reamer got off center with the burr and visibly wobbled off center until it headspaced. I measured the chamber and it was 0.0050". I took it to the range and shot it anyway, along with the other rifles I did. The rifle shoots better than I can. I thought concentricity was important. That math and testing by A.A. Abbato had to do with ammo concentricity. [url=http://www.thehighroad.org/archive/index.php/t-617604.html]Concentricity - How much more accurate? - THR[/url] It turns out that run out in ammo is rotationally randomly inserted, while run out in chamber is consistent, and throws bullets off center in the same direction into the same small group. It sometimes angers gunsmiths when I point this out. They wasted their whole lives dialing in barrels. But it is a one time cost, no harm no foul. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Gunsmithing
Why dial a rifle bore within .0001"
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