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Rifles, Reloading, Optics, Equipment
Reloading
Reading a sinclair concentricity gauge
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<blockquote data-quote="redleg1013" data-source="post: 1617852" data-attributes="member: 49994"><p>Not to get all GD&T, but let's not get roundness (circularity) convoluted with concentricity and runout.</p><p>If there is case wall variation, forget it, unless you map out the inconsistencies and then verify with an indicator, you're going to go mad chasing your tail looking for concentricity... tighten up on the circularity of the neck. Indicate along the case, if the case is banana shaped, you're going to again chase your tail since you won't know uf the case is causing the runout or the neck or both (at least not without devoting a fair bit of time per case). To put things simply runout = circularity + concentricity. You have to have one of them controlled, and let's face it, it is a LOT easier to control circularity. Use quality dies in a rigid O-frame (or multi-axial) press to minimize induced runout due to flex when sizing brass, then turn your necks (good news is you only have to do it once) to a uniform dimension (knocking off the high spots is second best) using the most reasonably rigid setup you can muster.</p><p></p><p>But at the end of the day it is up to the end user. If, like me, OCD demands and time allows go for it. I FL size without the expander (tool deflection is a real thing) in my Forster CoAx press, then expand on a mandrel, neck turn on a lathe (Forster original case trimmer).</p></blockquote><p></p>
[QUOTE="redleg1013, post: 1617852, member: 49994"] Not to get all GD&T, but let's not get roundness (circularity) convoluted with concentricity and runout. If there is case wall variation, forget it, unless you map out the inconsistencies and then verify with an indicator, you're going to go mad chasing your tail looking for concentricity... tighten up on the circularity of the neck. Indicate along the case, if the case is banana shaped, you're going to again chase your tail since you won't know uf the case is causing the runout or the neck or both (at least not without devoting a fair bit of time per case). To put things simply runout = circularity + concentricity. You have to have one of them controlled, and let's face it, it is a LOT easier to control circularity. Use quality dies in a rigid O-frame (or multi-axial) press to minimize induced runout due to flex when sizing brass, then turn your necks (good news is you only have to do it once) to a uniform dimension (knocking off the high spots is second best) using the most reasonably rigid setup you can muster. But at the end of the day it is up to the end user. If, like me, OCD demands and time allows go for it. I FL size without the expander (tool deflection is a real thing) in my Forster CoAx press, then expand on a mandrel, neck turn on a lathe (Forster original case trimmer). [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Reading a sinclair concentricity gauge
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