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Rifles, Reloading, Optics, Equipment
Reloading
Concentricity - setting up dies - runout
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<blockquote data-quote="boomtube" data-source="post: 504633" data-attributes="member: 9215"><p>Hornady's Concentricity gage has a way to hopefully bend a round straight. Okay. But I don't care for bending anything to correct an error, rather use my gages to find where the non-concentricity comes in an fix it there.</p><p> </p><p>Several things contribute to runout, I've never found "die set up", as such, to be a big issue. </p><p> </p><p>Bad case necks, that is non-concentic necks, is the biggest factor. If the necks aren't straight no die can make them so. For factory (loose) chambers, lightly skim turning necks will improve the consistancy but making the mecks too thin adds it's own problems to the already loose fit.</p><p> </p><p>It helps if the expander ball is bullet diameter or no more than a thou smaller. Most sizers squeeze case necks much too small and then we drag a short expander ball back out. That extraction pull tends to drift to the thin/soft side and pulls a formally straight neck to an offset angle; not good! Using an outside expander die/plug that pushes in rather than out, such as Lyman's "M" expander helps a lot.</p><p> </p><p>Excessive 'bullet tension', any more than maybe 2 thou, frequently causes bullets to tilt during seating. No presumed tricks such as seating part way, turning the case and completing seating can do anything significant to reduce it either, the die's internal fit is usually too loose for that to really matter.</p><p> </p><p>I LOVE Lee's collet neck sizers, they do not make the necks too small (So, some owners insist on grinding the inner mandrel down to make it so!). The collet fingers work to make the ID correct for best seating AND does it in such a way as to leave the sized necks about as straight as the brass itself will permit. The Lee collet has a moving part and that seems to buffalo some users but anyone willing to learn to use it correctly will be happy.</p><p> </p><p>When I need to FL size my precision cases I use a body die and finish with the Lee Neck Die. </p><p> </p><p>It is possible to use a "bushing" type neck die but all that can do is make the external neck diameter consistant. If the necks are not turned to a consistant thickness the difference will be forced inside and that will cause variation in bullet grip and that is NOT good for accuracy! Many bushing die users want a 'high bullet tension' (more than 2 thou,) and that increases the average runout from seating in a too tight neck.</p><p> </p><p>With good necks, properly sized, a really good seater finishes the job. ONLY the Forster BR and Redding Competition dies have a "staight line" seater design. Their heavy inner spring loaded guide sleeve fully contains both the bullet and case in line before seating starts. (The various micrometer type seating heads are user helps only, they do nothing to make the ammo straighter.)</p></blockquote><p></p>
[QUOTE="boomtube, post: 504633, member: 9215"] Hornady's Concentricity gage has a way to hopefully bend a round straight. Okay. But I don't care for bending anything to correct an error, rather use my gages to find where the non-concentricity comes in an fix it there. Several things contribute to runout, I've never found "die set up", as such, to be a big issue. Bad case necks, that is non-concentic necks, is the biggest factor. If the necks aren't straight no die can make them so. For factory (loose) chambers, lightly skim turning necks will improve the consistancy but making the mecks too thin adds it's own problems to the already loose fit. It helps if the expander ball is bullet diameter or no more than a thou smaller. Most sizers squeeze case necks much too small and then we drag a short expander ball back out. That extraction pull tends to drift to the thin/soft side and pulls a formally straight neck to an offset angle; not good! Using an outside expander die/plug that pushes in rather than out, such as Lyman's "M" expander helps a lot. Excessive 'bullet tension', any more than maybe 2 thou, frequently causes bullets to tilt during seating. No presumed tricks such as seating part way, turning the case and completing seating can do anything significant to reduce it either, the die's internal fit is usually too loose for that to really matter. I LOVE Lee's collet neck sizers, they do not make the necks too small (So, some owners insist on grinding the inner mandrel down to make it so!). The collet fingers work to make the ID correct for best seating AND does it in such a way as to leave the sized necks about as straight as the brass itself will permit. The Lee collet has a moving part and that seems to buffalo some users but anyone willing to learn to use it correctly will be happy. When I need to FL size my precision cases I use a body die and finish with the Lee Neck Die. It is possible to use a "bushing" type neck die but all that can do is make the external neck diameter consistant. If the necks are not turned to a consistant thickness the difference will be forced inside and that will cause variation in bullet grip and that is NOT good for accuracy! Many bushing die users want a 'high bullet tension' (more than 2 thou,) and that increases the average runout from seating in a too tight neck. With good necks, properly sized, a really good seater finishes the job. ONLY the Forster BR and Redding Competition dies have a "staight line" seater design. Their heavy inner spring loaded guide sleeve fully contains both the bullet and case in line before seating starts. (The various micrometer type seating heads are user helps only, they do nothing to make the ammo straighter.) [/QUOTE]
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Concentricity - setting up dies - runout
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