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Rifles, Reloading, Optics, Equipment
Reloading
Sinclair Concentricity Gauge
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<blockquote data-quote="TRexF16" data-source="post: 2375365" data-attributes="member: 108912"><p>Well, yes, because most of the time it's the case neck to case body relationship that's the culprit. Often it's not the bullet so much that has the runout as the case. I find that if a case is straight, and I have my dies adjusted well with a seating stem that matches the profile of my bullet (which you can custom make for yourself with some epoxy), then the bullet will be straight too, and vice versa. IF the cases are very straight but the loaded round has bullet runout, I would be exploring fixes to the seating process. So, back to your question:</p><p></p><p>If you look at how a concentricity gauge works when you're measuring case neck runout (no bullet loaded yet), it is basically measuring the misalignment of the case neck to the case body. Let's say that's .003 "TIR." You seat your bullet, use the gauge to check the runout now and it's .004, which isn't too bad since you only induced a thou in seating the bullet, and that might just be because you're moving the measurement point further from the case. As you roll the cartridge around in the gauge, note the point where the needle on your dial indicator (or the digits for yuppie digital guys - LOL) is at its lowest value. Slide the cartridge into the appropriate hole with the same side "up" that was "up" when your TIR readout was at its least. With the heel of your hand braced against the benchtop, use your fingers to put a slight upward pressure on the case body. Then put it back on the gauge and check the new runout. It's subtle, but you will very quickly get the feel for it. it is pretty easy to get a cartridge that has some runout, no matter how much, down to the .001 range. I could swear I have seen a video of this being done but a search is not succeeding now. There are a couple threads on the 24 hour campfire about it, and the tool is also sometimes called Tru angle.</p><p></p><p>Hope this helps,</p><p>Rex</p></blockquote><p></p>
[QUOTE="TRexF16, post: 2375365, member: 108912"] Well, yes, because most of the time it's the case neck to case body relationship that's the culprit. Often it's not the bullet so much that has the runout as the case. I find that if a case is straight, and I have my dies adjusted well with a seating stem that matches the profile of my bullet (which you can custom make for yourself with some epoxy), then the bullet will be straight too, and vice versa. IF the cases are very straight but the loaded round has bullet runout, I would be exploring fixes to the seating process. So, back to your question: If you look at how a concentricity gauge works when you're measuring case neck runout (no bullet loaded yet), it is basically measuring the misalignment of the case neck to the case body. Let's say that's .003 "TIR." You seat your bullet, use the gauge to check the runout now and it's .004, which isn't too bad since you only induced a thou in seating the bullet, and that might just be because you're moving the measurement point further from the case. As you roll the cartridge around in the gauge, note the point where the needle on your dial indicator (or the digits for yuppie digital guys - LOL) is at its lowest value. Slide the cartridge into the appropriate hole with the same side "up" that was "up" when your TIR readout was at its least. With the heel of your hand braced against the benchtop, use your fingers to put a slight upward pressure on the case body. Then put it back on the gauge and check the new runout. It's subtle, but you will very quickly get the feel for it. it is pretty easy to get a cartridge that has some runout, no matter how much, down to the .001 range. I could swear I have seen a video of this being done but a search is not succeeding now. There are a couple threads on the 24 hour campfire about it, and the tool is also sometimes called Tru angle. Hope this helps, Rex [/QUOTE]
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Sinclair Concentricity Gauge
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