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Rifles, Reloading, Optics, Equipment
Reloading
Hornady or Sinclair concentricity guage
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<blockquote data-quote="B-P-UU" data-source="post: 449619" data-attributes="member: 29114"><p><span style="font-size: 12px">This thread brought me out of the woodworks. Hello, I've been absorbing a lot of info from this site for a long time; truly great stuff. I would like to start off by saying I personally own none of the tools mentioned on this thread, so take this for what it's worth. I reload, just not to the level of some of the members of this site. I do, however, have experience applying runout to engineering prints.</span></p><p><span style="font-size: 12px">MikeCR is 100% correct in stating "if you eliminate runout, your ammo will be concentric." The converse is not true, however; you can be 100% concentric and have lots of runout, as he also mentioned. </span></p><p><span style="font-size: 12px">By definition (ASME Y14.5 GD&T Standard), the proper way to measure runout is by chucking the sample (in this case, a loaded round) via the datum you are comparing your dial indicator to (in the case of a loaded round, the case head) to find the center axis of the case (sorry, tried attaching pic to clear this up). Thus, the Sinclair tool mentioned does not actually measure runout; it references datum points on the case surface via rollers as opposed to referencing the case axis, the theoretical center of the case. To visualize this, imagine if the piece of brass was egg shaped. When rolling the loaded round, your dial indicator on the bullet would give readings all over the place. In that example, it is also possible the bullet is 100% concentric with the 'egg' shaped brass, even though your dial indicator says otherwise. While that may not be a likely scenario, dents or imperfections on the case body is. These imperfections would also show up on your indicator as 'false runout'. </span></p><p><span style="font-size: 12px">From what I can tell, the Sinclair tool and tools like it are actually measuring bullet position with respect to the OD surface of the case as the reference datum. This isn't necessarily a bad thing, it just is not runout. </span></p><p><span style="font-size: 12px">Unlike concentricity, runout also controls feature shape (roundness). In reloading, regardless of the measurement device used, you are making one fairly safe assumption: the bullet is perfectly round. God himself can prep your brass, but if your bullets are out of round, i.e., surface imperfections or a lobed surface (triangular w/ rounded corners), your dial indicator will bounce around. </span></p><p><span style="font-size: 12px">Concentricity is much more difficult to control and measure. If dial indicators are used to measure concentricity, you really need two of them to do so. The dial indicators need to be 180 degrees apart and the case needs to be rotated, collecting data points each time you stop (this can be every 45 degrees, 15 degrees, etc.). Once data points are collected, the median points of the tolerance feature (bullet) must be within the tolerance zone of the case datum axis. Fuzzy? On a loaded round, you would need to collect data on the case as described above, calculate the center based on that data (MATH), then do the same for the bullet and compare the two values. CMM's are often used for this, collecting 100's to 1000's of points. The points are generated and math functions in the CMM are used to give you a magic 'center' number. These two 'center' numbers are then compared to the specified tolerance. Most reloading benches I've seen do not have CMM's.</span></p><p><span style="font-size: 12px">For what it's worth, every time I've seen concentricity specified on a print, the author really means runout. Most shops don't understand concentricity well enough to accurately/reliably measure it – they can measure runout fairly easily though. Even the ASME Y14.5 Standard recommends using runout or true position instead of concentricity. The reason; it is often misused. </span></p><p><span style="font-size: 12px">Finally, I cringe every time I hear someone say 'total runout' when measuring bullets with respect to the case. Total runout is measured similarly to runout with one exception; the dial indicator must be moved horizontally along the measured surface. Total runout applies to the ENTIRE surface. Although they seem similar, total runout controls concentricity, straightness, roundness, and taper. This is a big deal. Unless your bullets are perfectly straight with respect to case datum axis (achievable), round (achievable), concentric (tricky, but doable), and have zero taper (a bullet without an ogive), you are correct. If your bullets curve to a point like mine, you are measuring runout. </span></p><p><span style="font-size: 12px">Looking purely at the design of Sinclair vs. Hornady, I would buy the Hornady to measure/correct bullet runout (with that being said, I have no idea what the gauge R&R is of either companies dial indicators – maybe they're both junk??). But if the runout is actually in the case mouth, the Hornady tool cannot correct that; that would need to be corrected by your die setup. </span></p><p><span style="font-size: 12px">I hope I have not further confused those already confused or angered those who are shooting ridiculously small groups with their current setups. Good Luck. </span></p></blockquote><p></p>
[QUOTE="B-P-UU, post: 449619, member: 29114"] [SIZE=3]This thread brought me out of the woodworks. Hello, I’ve been absorbing a lot of info from this site for a long time; truly great stuff. I would like to start off by saying I personally own none of the tools mentioned on this thread, so take this for what it’s worth. I reload, just not to the level of some of the members of this site. I do, however, have experience applying runout to engineering prints.[/SIZE] [SIZE=3]MikeCR is 100% correct in stating “if you eliminate runout, your ammo will be concentric.” The converse is not true, however; you can be 100% concentric and have lots of runout, as he also mentioned. [/SIZE] [SIZE=3]By definition (ASME Y14.5 GD&T Standard), the proper way to measure runout is by chucking the sample (in this case, a loaded round) via the datum you are comparing your dial indicator to (in the case of a loaded round, the case head) to find the center axis of the case (sorry, tried attaching pic to clear this up). Thus, the Sinclair tool mentioned does not actually measure runout; it references datum points on the case surface via rollers as opposed to referencing the case axis, the theoretical center of the case. To visualize this, imagine if the piece of brass was egg shaped. When rolling the loaded round, your dial indicator on the bullet would give readings all over the place. In that example, it is also possible the bullet is 100% concentric with the ‘egg’ shaped brass, even though your dial indicator says otherwise. While that may not be a likely scenario, dents or imperfections on the case body is. These imperfections would also show up on your indicator as ‘false runout’. [/SIZE] [SIZE=3]From what I can tell, the Sinclair tool and tools like it are actually measuring bullet position with respect to the OD surface of the case as the reference datum. This isn’t necessarily a bad thing, it just is not runout. [/SIZE] [SIZE=3]Unlike concentricity, runout also controls feature shape (roundness). In reloading, regardless of the measurement device used, you are making one fairly safe assumption: the bullet is perfectly round. God himself can prep your brass, but if your bullets are out of round, i.e., surface imperfections or a lobed surface (triangular w/ rounded corners), your dial indicator will bounce around. [/SIZE] [SIZE=3]Concentricity is much more difficult to control and measure. If dial indicators are used to measure concentricity, you really need two of them to do so. The dial indicators need to be 180 degrees apart and the case needs to be rotated, collecting data points each time you stop (this can be every 45 degrees, 15 degrees, etc.). Once data points are collected, the median points of the tolerance feature (bullet) must be within the tolerance zone of the case datum axis. Fuzzy? On a loaded round, you would need to collect data on the case as described above, calculate the center based on that data (MATH), then do the same for the bullet and compare the two values. CMM’s are often used for this, collecting 100’s to 1000’s of points. The points are generated and math functions in the CMM are used to give you a magic ‘center’ number. These two ‘center’ numbers are then compared to the specified tolerance. Most reloading benches I’ve seen do not have CMM’s.[/SIZE] [SIZE=3]For what it’s worth, every time I’ve seen concentricity specified on a print, the author really means runout. Most shops don’t understand concentricity well enough to accurately/reliably measure it – they can measure runout fairly easily though. Even the ASME Y14.5 Standard recommends using runout or true position instead of concentricity. The reason; it is often misused. [/SIZE] [SIZE=3]Finally, I cringe every time I hear someone say ‘total runout’ when measuring bullets with respect to the case. Total runout is measured similarly to runout with one exception; the dial indicator must be moved horizontally along the measured surface. Total runout applies to the ENTIRE surface. Although they seem similar, total runout controls concentricity, straightness, roundness, and taper. This is a big deal. Unless your bullets are perfectly straight with respect to case datum axis (achievable), round (achievable), concentric (tricky, but doable), and have zero taper (a bullet without an ogive), you are correct. If your bullets curve to a point like mine, you are measuring runout. [/SIZE] [SIZE=3]Looking purely at the design of Sinclair vs. Hornady, I would buy the Hornady to measure/correct bullet runout (with that being said, I have no idea what the gauge R&R is of either companies dial indicators – maybe they’re both junk??). But if the runout is actually in the case mouth, the Hornady tool cannot correct that; that would need to be corrected by your die setup. [/SIZE] [SIZE=3]I hope I have not further confused those already confused or angered those who are shooting ridiculously small groups with their current setups. Good Luck. [/SIZE] [/QUOTE]
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Hornady or Sinclair concentricity guage
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