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Rifles, Reloading, Optics, Equipment
Reloading
newbie question about case trimming
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<blockquote data-quote="AZShooter" data-source="post: 900579" data-attributes="member: 5219"><p>No need to trim often if you know the length of your chamber. If you have a custom you should be able to inquire about the reamer dimensions. If you can't do that you can measure the distance to the end of the chamber with Sinclair's chamber length plugs: </p><p></p><p><a href="http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx" target="_blank">Sinclair Chamber Length Gage | Sinclair Intl</a></p><p></p><p>To understand the concept read this from Varmint Al's webpage:</p><p></p><p></p><p>"MEASURE THE CHAMBER LENGTH.... Purchase the Sinclair case length measuring plugs. These are very simple steel cylinders turned to the bullet diameter, leaving a rim slightly less than the case neck OD. Trim the case length about 0.100 inch short so the case mouth will not touch the rim of the plug gauge. Insert the Sinclair plug gauge as if it were a bullet, leaving it long and then chamber the case. The plug will be pushed deeper into the case neck and when you extract it, you can measure the chamber's actual length with a dial caliper. I usually find that the factory recommendations for case length leave a 0.050 inch to 0.070 inch gap between the end of the case and the actual length of the chamber. This is a factory safety concern and you can get high pressures by forcing a long case into a short chamber. The factory wants to be on the safe side. But like everything else, if you want the best accuracy, you can minimize this gap down to 0.005 inch and still be safe. "</p><p></p><p>I have found that some factory chambers are .070" or longer than SAMMI max length. I keep a reference chart in my reloading room on all my rifle's chamber lengths. Except for trueing new brass, case trimming is a rare event for a factory chamber. The custom chambers are usually shorter.</p></blockquote><p></p>
[QUOTE="AZShooter, post: 900579, member: 5219"] No need to trim often if you know the length of your chamber. If you have a custom you should be able to inquire about the reamer dimensions. If you can't do that you can measure the distance to the end of the chamber with Sinclair's chamber length plugs: [url=http://www.sinclairintl.com/reloading-equipment/measuring-tools/case-gauges-headspace-tools/sinclair-chamber-length-gage-prod32925.aspx]Sinclair Chamber Length Gage | Sinclair Intl[/url] To understand the concept read this from Varmint Al's webpage: "MEASURE THE CHAMBER LENGTH.... Purchase the Sinclair case length measuring plugs. These are very simple steel cylinders turned to the bullet diameter, leaving a rim slightly less than the case neck OD. Trim the case length about 0.100 inch short so the case mouth will not touch the rim of the plug gauge. Insert the Sinclair plug gauge as if it were a bullet, leaving it long and then chamber the case. The plug will be pushed deeper into the case neck and when you extract it, you can measure the chamber's actual length with a dial caliper. I usually find that the factory recommendations for case length leave a 0.050 inch to 0.070 inch gap between the end of the case and the actual length of the chamber. This is a factory safety concern and you can get high pressures by forcing a long case into a short chamber. The factory wants to be on the safe side. But like everything else, if you want the best accuracy, you can minimize this gap down to 0.005 inch and still be safe. " I have found that some factory chambers are .070" or longer than SAMMI max length. I keep a reference chart in my reloading room on all my rifle's chamber lengths. Except for trueing new brass, case trimming is a rare event for a factory chamber. The custom chambers are usually shorter. [/QUOTE]
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newbie question about case trimming
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