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Rifles, Reloading, Optics, Equipment
Reloading
True Concentricity Gauge?
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<blockquote data-quote="Bart B" data-source="post: 637844" data-attributes="member: 5302"><p>The best concentricity gage I know of is one made by me that cost less than $2 in materials plus a cheap dial indicator.</p><p></p><p>Two 1/4" threaded rods 7 inches long with a V block at its back end for the case's pressure ring to ride in. Up front was a nylon washer held in the rods with a 3/8 inch hole in it. That washer's aligned such that its center is pretty much in line with .470 and .510 inch diameter case centers as they rest in the V block.</p><p></p><p>30 caliber rounds (.308 Win, .30-06 and two 30 caliber magnums) would be put in, back end resting in the V block and their shoulder pushed into the washer. That nylon washer could be moved back and forth so it puts the case pressure ring on the V block when the case shoulder's centered against it. Dial indicator plunger would be put about 1/10th inch back from bullet tip.</p><p></p><p>With the case's pressure ring resting in the V block and pushed forward seating its shoulder in the washer hole, that's how the case fits the chamber when it fires; its shoulder's centered in the chamber shoulder and the back end's pushed sideways against the chamber wall by the extractor. Any out of round caused by an oval- or egg-shaped case body at or near the shoulder doesn't effect the readings; full length sized cases ensure plenty of clearance between case body and chamber at the case shoulder.</p></blockquote><p></p>
[QUOTE="Bart B, post: 637844, member: 5302"] The best concentricity gage I know of is one made by me that cost less than $2 in materials plus a cheap dial indicator. Two 1/4" threaded rods 7 inches long with a V block at its back end for the case's pressure ring to ride in. Up front was a nylon washer held in the rods with a 3/8 inch hole in it. That washer's aligned such that its center is pretty much in line with .470 and .510 inch diameter case centers as they rest in the V block. 30 caliber rounds (.308 Win, .30-06 and two 30 caliber magnums) would be put in, back end resting in the V block and their shoulder pushed into the washer. That nylon washer could be moved back and forth so it puts the case pressure ring on the V block when the case shoulder's centered against it. Dial indicator plunger would be put about 1/10th inch back from bullet tip. With the case's pressure ring resting in the V block and pushed forward seating its shoulder in the washer hole, that's how the case fits the chamber when it fires; its shoulder's centered in the chamber shoulder and the back end's pushed sideways against the chamber wall by the extractor. Any out of round caused by an oval- or egg-shaped case body at or near the shoulder doesn't effect the readings; full length sized cases ensure plenty of clearance between case body and chamber at the case shoulder. [/QUOTE]
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True Concentricity Gauge?
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