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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
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<blockquote data-quote="goodgrouper" data-source="post: 208880" data-attributes="member: 2852"><p>Ok. Now we need more information. You mean on any given load, you have 110 fps extreme spread? If so, that would indicate you might have a standard deviation of 50 fps or more. A load with that kind of inconsistency might shoot good one day but it will not usually repeat it's performance again. Also, you need to look for nodes or loading windows (also called sweet spots) in the overall load ladder. These are indicated by low deviations were the ignition of the powder column is at a most efficient point. There are usually two nodes. ONe at a low pressure, and one at a high pressure. In my experience of working on many 7mm mags is that they usually have the best performance at the higher pressure node which is around 3000 to 3050 fps with a 160 grain bullet. So my guess is that you are inbetween the two nodes right now and therefore have crappy, inconsistent performance.</p><p></p><p>Then once you find a powder charge that yeilds low variations in speed, then tinker with seating depths. Accubonds are notorious for liking quite a bit of "jump" to the riflings. So load them to fit in the magazine (if being used for hunting) and then seat them deeper into the case in .005" increments. In this method, you will get good velocity uniformity and shrink the groups up a bit.</p><p></p><p>I just also saw that your gun is not bedded. You really ought to get this done for accuracy consistency too.</p></blockquote><p></p>
[QUOTE="goodgrouper, post: 208880, member: 2852"] Ok. Now we need more information. You mean on any given load, you have 110 fps extreme spread? If so, that would indicate you might have a standard deviation of 50 fps or more. A load with that kind of inconsistency might shoot good one day but it will not usually repeat it's performance again. Also, you need to look for nodes or loading windows (also called sweet spots) in the overall load ladder. These are indicated by low deviations were the ignition of the powder column is at a most efficient point. There are usually two nodes. ONe at a low pressure, and one at a high pressure. In my experience of working on many 7mm mags is that they usually have the best performance at the higher pressure node which is around 3000 to 3050 fps with a 160 grain bullet. So my guess is that you are inbetween the two nodes right now and therefore have crappy, inconsistent performance. Then once you find a powder charge that yeilds low variations in speed, then tinker with seating depths. Accubonds are notorious for liking quite a bit of "jump" to the riflings. So load them to fit in the magazine (if being used for hunting) and then seat them deeper into the case in .005" increments. In this method, you will get good velocity uniformity and shrink the groups up a bit. I just also saw that your gun is not bedded. You really ought to get this done for accuracy consistency too. [/QUOTE]
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