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Rifles, Reloading, Optics, Equipment
Reloading
Measuring to the lands
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<blockquote data-quote="Bart B" data-source="post: 1122831" data-attributes="member: 5302"><p>That link (Getting the Best Precision and Accuracy .....) echos what lots of folks do. But it has one huge flaw and one medium flaw.</p><p></p><p>Anyone who thinks one or two 3-shot groups will represent the real accuracy level of any load needs to bone up on ballistic statistics. A single 3-shot group has about a 1 in 15 (or worse) chance of showing the area all fired shots will land in. Two of them superimposed to represent a 6-shot group has about a 1 in 10 change of representing real accuracy. This is for the rifle being shot in free recoil. Strings of 5-shot groups fired at short ranges in 100-yd. benchrest matches from the same rifle range from a few hundredths to one-third inch or more to hold aggregate records. And their shot in no particular order of group size.</p><p></p><p>If a human holds the rifle against their shoulder, the odds get worse. However, if you can shoot ten 3-shot groups that are within 10% of the same size, then shooting one will suffice.</p><p></p><p>Keeping cartridge OAL to a .001" spread means nothing. Bullet tip distance from the rifling contact point on its ogive will vary a lot more than that. And if all the bottleneck cases have a spread of case headspace, the bullet contact point distance from the rifling will also have at least that much spread in distance.</p></blockquote><p></p>
[QUOTE="Bart B, post: 1122831, member: 5302"] That link (Getting the Best Precision and Accuracy .....) echos what lots of folks do. But it has one huge flaw and one medium flaw. Anyone who thinks one or two 3-shot groups will represent the real accuracy level of any load needs to bone up on ballistic statistics. A single 3-shot group has about a 1 in 15 (or worse) chance of showing the area all fired shots will land in. Two of them superimposed to represent a 6-shot group has about a 1 in 10 change of representing real accuracy. This is for the rifle being shot in free recoil. Strings of 5-shot groups fired at short ranges in 100-yd. benchrest matches from the same rifle range from a few hundredths to one-third inch or more to hold aggregate records. And their shot in no particular order of group size. If a human holds the rifle against their shoulder, the odds get worse. However, if you can shoot ten 3-shot groups that are within 10% of the same size, then shooting one will suffice. Keeping cartridge OAL to a .001" spread means nothing. Bullet tip distance from the rifling contact point on its ogive will vary a lot more than that. And if all the bottleneck cases have a spread of case headspace, the bullet contact point distance from the rifling will also have at least that much spread in distance. [/QUOTE]
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Reloading
Measuring to the lands
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