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Rifles, Reloading, Optics, Equipment
Reloading
Which comes first, the chicken or the egg? Charge weight or seating depth…
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<blockquote data-quote="QuietTexan" data-source="post: 2274713" data-attributes="member: 116181"><p>The Hornady tool is not the most precise thing ever made. That's why the whole set of them costs less than a single comparator from SAC. The hole on the 6.5mm Hornady tool is going to be something like 0.250", even though a 6.5MM barrel is .264" across the bottom of the grooves, and 0.256" across the lands. The bullet will interface with the lands somewhere between those two measurements depending on how the reamer cut the chamber, but the tool does not measure that exact point. The tool measures some arbitrary distance in front of that point which is consistent enough for a single bullet, but doesn't work across different models of bullets. The SAC comparator notionally does measure the interface point by using a 3° angle between 0.256" and 0.266" to mimic a chamber, but then there will still be a difference between the tool and what the eroded throat of a particular rifle looks like. It doesn't matter so long as you measure the seating depth of each different bullet you load on your tool.</p><p>[URL unfurl="true"]https://www.shortactioncustoms.com/modular-headspace-comparator-inserts-1[/URL]</p><p></p><p></p><p></p><p>Typos aside, in my 300 RUM seating a Berger 210 to the generic book COL in the manual of 3.600" is a jump of 0.229". I seem to recall Berger having a caveat at the front of the book about testing seating depths though <img class="smilie smilie--emoji" loading="lazy" alt="🤡" title="Clown face :clown:" src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f921.png" data-shortname=":clown:" /> Touching the lands is basically 3.900" COL.</p></blockquote><p></p>
[QUOTE="QuietTexan, post: 2274713, member: 116181"] The Hornady tool is not the most precise thing ever made. That's why the whole set of them costs less than a single comparator from SAC. The hole on the 6.5mm Hornady tool is going to be something like 0.250", even though a 6.5MM barrel is .264" across the bottom of the grooves, and 0.256" across the lands. The bullet will interface with the lands somewhere between those two measurements depending on how the reamer cut the chamber, but the tool does not measure that exact point. The tool measures some arbitrary distance in front of that point which is consistent enough for a single bullet, but doesn't work across different models of bullets. The SAC comparator notionally does measure the interface point by using a 3° angle between 0.256" and 0.266" to mimic a chamber, but then there will still be a difference between the tool and what the eroded throat of a particular rifle looks like. It doesn't matter so long as you measure the seating depth of each different bullet you load on your tool. [URL unfurl="true"]https://www.shortactioncustoms.com/modular-headspace-comparator-inserts-1[/URL] Typos aside, in my 300 RUM seating a Berger 210 to the generic book COL in the manual of 3.600" is a jump of 0.229". I seem to recall Berger having a caveat at the front of the book about testing seating depths though 🤡 Touching the lands is basically 3.900" COL. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Which comes first, the chicken or the egg? Charge weight or seating depth…
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