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Rifles, Reloading, Optics, Equipment
Reloading
Why is primer seating important?
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<blockquote data-quote="Mikecr" data-source="post: 1806484" data-attributes="member: 1521"><p>There is more to it than leaving short, or bottoming in contrast. There is more to it than anybody can 'feel' (even with the $$$ tools).</p><p>Primer manufacturers recommend 2thou crush. That is touch bottoming + 0.002" further. I have found over the years that Feds/Wins/Rems like 2thou, but CCIs like 5thou crush. CCIs do not provide the same grouping results for me at 2thou crush.</p><p>There is another issue in this, in that primers back out over time. Before I go hunting with ammo made 6mos earlier, I re-seat them 1thou, and so far this has worked well.</p><p></p><p>You can't feel this kind of precision, and anyone who measures it learns this much for sure. But seating to bottom by feel does at least provide reliable function, and I'm pretty sure most people assume that primers fire the same if they fire at all..</p><p>That is not true.</p><p></p><p>You may have noticed while reviewing attributes of primers, that it's common to wholesale swap them, searching for best results. Also, that there are sometimes lot-to-lot differences causing setback in tune.</p><p>This is not one primer actually being better than another due to case capacity or powder. The test for that fails while we end up using different primers for the same cartridges and powders.</p><p>What passes tests here is different (possibly unique) striking from each shooting system. It's my contention, because I've seen it, that you can pick any primer and tune the striking for optimum results -from that primer.</p><p></p><p>Primer striking is difficult science. I'm aware of very little information out there about it, and zero standards. But for sure, primer seating affects the outcome, regardless of your striking.</p><p>I have a Taurus pistol in 38spec that happens to be very very accurate. Unfortunately it is just as unreliable as accurate. It has a headspace issue causing ~99% of ammo available to misfire. This, even with full indentation of misfire primers.</p><p>The difference in measure between reliable firing and failed is 3thou rim thickness!</p><p>And get this: a 2thou thicker rim(1thou under confirmed reliable) will fire nearly every one, but these shots are thrown from grouping..</p><p></p><p>Headspace and striking are important, and if you care to measure seating to crush there is only one tool to do so: the Indicated K&M seater.</p><p>It's also a pretty good seater, measurement aside.</p><p>I also uniform primer pocket depths to help with consistent striking. Sinclair offers a really good tool for that.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1806484, member: 1521"] There is more to it than leaving short, or bottoming in contrast. There is more to it than anybody can 'feel' (even with the $$$ tools). Primer manufacturers recommend 2thou crush. That is touch bottoming + 0.002" further. I have found over the years that Feds/Wins/Rems like 2thou, but CCIs like 5thou crush. CCIs do not provide the same grouping results for me at 2thou crush. There is another issue in this, in that primers back out over time. Before I go hunting with ammo made 6mos earlier, I re-seat them 1thou, and so far this has worked well. You can't feel this kind of precision, and anyone who measures it learns this much for sure. But seating to bottom by feel does at least provide reliable function, and I'm pretty sure most people assume that primers fire the same if they fire at all.. That is not true. You may have noticed while reviewing attributes of primers, that it's common to wholesale swap them, searching for best results. Also, that there are sometimes lot-to-lot differences causing setback in tune. This is not one primer actually being better than another due to case capacity or powder. The test for that fails while we end up using different primers for the same cartridges and powders. What passes tests here is different (possibly unique) striking from each shooting system. It's my contention, because I've seen it, that you can pick any primer and tune the striking for optimum results -from that primer. Primer striking is difficult science. I'm aware of very little information out there about it, and zero standards. But for sure, primer seating affects the outcome, regardless of your striking. I have a Taurus pistol in 38spec that happens to be very very accurate. Unfortunately it is just as unreliable as accurate. It has a headspace issue causing ~99% of ammo available to misfire. This, even with full indentation of misfire primers. The difference in measure between reliable firing and failed is 3thou rim thickness! And get this: a 2thou thicker rim(1thou under confirmed reliable) will fire nearly every one, but these shots are thrown from grouping.. Headspace and striking are important, and if you care to measure seating to crush there is only one tool to do so: the Indicated K&M seater. It's also a pretty good seater, measurement aside. I also uniform primer pocket depths to help with consistent striking. Sinclair offers a really good tool for that. [/QUOTE]
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Why is primer seating important?
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