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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: 1122959" data-attributes="member: 5302"><p>bob4, from a ballistic statistical point of view, I think those three groups are equal in size. A three-shot group's size tell the shooter that 19 out of 20 of them will be anywhere from about 40% as big to about 245% larger. If the first 3-shot group is 1 inch extreme spread and you shoot 19 more of them, they'll typically range from about .4" to almost 2.5"</p><p></p><p>Take your favorite .22 rimfire to the range with 60 rounds ammo then shoot twenty 3-shot groups. See if each one's within 10% of the same size. If you shoot all 20 groups on top of a backer target, you'll have a 60-shot composite showing the real accuracy you can count on virtually all the time shooting that rifle with the ammo selected. It'll be bigger than the largest 3-shot group.</p><p></p><p>My basic rule for accuracy testing is, if several groups with the same shot count have more than a 10% spread in size, none of them represent the accuracy I can count on at least 90% of the time. The biggest one is close, though. Which is why I shoot at least 20 shots per test group. 30 is better. I want to know where all my fired shots will land relative to the aiming point; not just 5% of them which a 3-shot group shows.</p></blockquote><p></p>
[QUOTE="Bart B, post: 1122959, member: 5302"] bob4, from a ballistic statistical point of view, I think those three groups are equal in size. A three-shot group's size tell the shooter that 19 out of 20 of them will be anywhere from about 40% as big to about 245% larger. If the first 3-shot group is 1 inch extreme spread and you shoot 19 more of them, they'll typically range from about .4" to almost 2.5" Take your favorite .22 rimfire to the range with 60 rounds ammo then shoot twenty 3-shot groups. See if each one's within 10% of the same size. If you shoot all 20 groups on top of a backer target, you'll have a 60-shot composite showing the real accuracy you can count on virtually all the time shooting that rifle with the ammo selected. It'll be bigger than the largest 3-shot group. My basic rule for accuracy testing is, if several groups with the same shot count have more than a 10% spread in size, none of them represent the accuracy I can count on at least 90% of the time. The biggest one is close, though. Which is why I shoot at least 20 shots per test group. 30 is better. I want to know where all my fired shots will land relative to the aiming point; not just 5% of them which a 3-shot group shows. [/QUOTE]
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Reloading
Measuring to the lands
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