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Rifles, Reloading, Optics, Equipment
Reloading
Concentricity .. how important?
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<blockquote data-quote="bigedp51" data-source="post: 1439884" data-attributes="member: 28965"><p>Full length resizing reduces the effects of neck/bullet runout. The full length resized case body and neck do not touch the chamber walls. The case is supported in the rear by the bolt face and by the bullet in the throat.</p><p></p><p>NOTE, at the Whidden custom die website they tell you they get the most concentric resized cases with non-bushing full length dies.</p><p></p><p>Below German Salazar from the Rifleman Journal website. He is answering a question about partial full length resizing. And explaining the benefits of full length resizing and bullet runout.</p><p></p><p><span style="color: #0000b3">Reloading: Partial Neck Sizing</span></p><p><span style="color: #0000b3">by German A. Salazar</span></p><p><span style="color: #0000b3"><a href="http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html" target="_blank">http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html</a></span></p><p><span style="color: #0000b3"></span></p><p><span style="color: #0000b3">"Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway."</span></p><p><span style="color: #0000b3"></span></p><p><span style="color: #0000b3"><span style="color: #000000">I have the two runout gauges in the photo below a Hornady and RCBS concentricity gauges. The Red Hornady gauge holds the bullet like if it had been full length resized. Meaning holding the base of the case in the rear and by the bullet.</span></span></p><p></p><p><span style="color: #0000b3"><span style="color: #000000"> The RCBS gauge spins the case on its body and is more applicable for cases that are neck sized only. Meaning the case body will have more of a guiding effect on the bullet in the throat.</span></span></p><p></p><p><span style="color: #000000"><img src="https://i.imgur.com/ed6Mwd8.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></span></p><p><span style="color: #000000"></span></p><p><span style="color: #000000"><img src="https://i.imgur.com/p4gKFHe.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></span></p><p><span style="color: #000000"></span></p><p><span style="color: #000000">Click on the image below to enlarge by Kevin Thomas of Team Lapua USA, and read about the rat turd in the violin case. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" /></span></p><p><span style="color: #000000"></span></p><p><span style="color: #000000"><img src="https://i.imgur.com/Y3IiYL5.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></span></p><p><span style="color: #000000"></span></p><p><span style="color: #000000">Bottom line, the U.S. Military considers match grade ammo to have .003 or less bullet runout.</span></p><p><span style="color: #000000"></span></p><p> <span style="color: #000000"></span></p><p><span style="color: #0000b3"></span></p><p><span style="color: #0000b3"></span></p></blockquote><p></p>
[QUOTE="bigedp51, post: 1439884, member: 28965"] Full length resizing reduces the effects of neck/bullet runout. The full length resized case body and neck do not touch the chamber walls. The case is supported in the rear by the bolt face and by the bullet in the throat. NOTE, at the Whidden custom die website they tell you they get the most concentric resized cases with non-bushing full length dies. Below German Salazar from the Rifleman Journal website. He is answering a question about partial full length resizing. And explaining the benefits of full length resizing and bullet runout. [COLOR=#0000b3]Reloading: Partial Neck Sizing by German A. Salazar [URL]http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html[/URL] "Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway." [COLOR=#000000]I have the two runout gauges in the photo below a Hornady and RCBS concentricity gauges. The Red Hornady gauge holds the bullet like if it had been full length resized. Meaning holding the base of the case in the rear and by the bullet.[/COLOR][/COLOR] [COLOR=#0000b3][COLOR=#000000] The RCBS gauge spins the case on its body and is more applicable for cases that are neck sized only. Meaning the case body will have more of a guiding effect on the bullet in the throat.[/COLOR][/COLOR] [COLOR=#000000][IMG]https://i.imgur.com/ed6Mwd8.jpg[/IMG] [IMG]https://i.imgur.com/p4gKFHe.jpg[/IMG] Click on the image below to enlarge by Kevin Thomas of Team Lapua USA, and read about the rat turd in the violin case. ;) [IMG]https://i.imgur.com/Y3IiYL5.jpg[/IMG] Bottom line, the U.S. Military considers match grade ammo to have .003 or less bullet runout. [/COLOR] [COLOR=#0000b3] [/COLOR] [/QUOTE]
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