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Long Range Hunting & Shooting
coal question
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<blockquote data-quote="7magcreedmoor" data-source="post: 971642" data-attributes="member: 48559"><p>Try this if my other post wasn't helpful, or maybe just start with this. Berger recommends a COAL test that involves using four different lengths. If you can touch the lands, start with one batch .010" off, the next batch .050", the next batch .090", and finally .130" off the lands. The key is using a comparator to measure the cartridge base-to-ogive consistently, as bullet shapes and the resulting length to the actual tip (meplat) can vary quite a bit. I suppose the term we really should be using is CBTO, not COAL. If you cannot load long enough to touch the lands, they recommend starting at the other end: load the first batch to SAAMI spec length, then each successive batch .040" longer, for four increments. Shoot for groups with each batch, and one will show noticeably better accuracy than the rest. Fine tune around that particular CBTO. My earlier post was more for measuring when you don't have a comparator to fit your bullet, and the Stony Point/Hornady tool to go with it.</p></blockquote><p></p>
[QUOTE="7magcreedmoor, post: 971642, member: 48559"] Try this if my other post wasn't helpful, or maybe just start with this. Berger recommends a COAL test that involves using four different lengths. If you can touch the lands, start with one batch .010" off, the next batch .050", the next batch .090", and finally .130" off the lands. The key is using a comparator to measure the cartridge base-to-ogive consistently, as bullet shapes and the resulting length to the actual tip (meplat) can vary quite a bit. I suppose the term we really should be using is CBTO, not COAL. If you cannot load long enough to touch the lands, they recommend starting at the other end: load the first batch to SAAMI spec length, then each successive batch .040" longer, for four increments. Shoot for groups with each batch, and one will show noticeably better accuracy than the rest. Fine tune around that particular CBTO. My earlier post was more for measuring when you don't have a comparator to fit your bullet, and the Stony Point/Hornady tool to go with it. [/QUOTE]
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