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Rifles, Reloading, Optics, Equipment
Reloading
3 shot groups…
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<blockquote data-quote="Doom2" data-source="post: 2854695" data-attributes="member: 108323"><p>Three shots @ 100yds can tell you a lot, a little, or they can tell you nearly nothing. For a hunting application three shot groups can tell you about where your zero is and what kind of distribution (grouping/point of impact you might expect with factory ammunition or a known good reload. But it does little to verify longer range performance and trajectory. For load development they can be useful in such methods as Newberry's OCW method where a group of two or three 3-shot groups have similar points of impact indicate a load insensitive to large POI shift for small charge increments. Three shots at 100yds with a good known load by a top level benchrech or F Class shooter can probably tell you what the rifle/ammo is capable of. Probably not for the other 95% of us.</p><p></p><p>Three shots over a chronograph. Is average velocity around 2800 fps or 2900 fps. Probably doable. Is the average 2900 or 2920? Probably not. Is the 5 standard deviation of one group really better than another with a 10 SD? Don't bet your paycheck or 2 cents on that one.</p><p></p><p>Ultimately what matters is what information you are trying to obtain and understanding what the limitations of are. You can't obtain detailed meaningful statistics from a 3 shot group over a chronograph. You can determine some on target information. You very likely cannot obtain real world group sizes for larger groups than the one that you shot. On target data also must consider the type of firearm that is used. A sporter barrel may put 3 shots touching but throw the next two. It's not designed to be a target rifle but a lightweight, luggable instrument capable of putting two or three rounds into the vital zone of animal. Dispersion at longer distance? Probably a good estimate if you have doped your distances. </p><p></p><p>Meaningful data is inherently related to what you intend to use the rifle for. For a hunting rifle worrying about a 5 shot group can lead you astray since the important shots or usually the first one or two. If shooting F-class or bench rest then it's important to know what the rifle and ammunition do for the course of fire. A three shot group in and of itself probably doesn't mean much.</p></blockquote><p></p>
[QUOTE="Doom2, post: 2854695, member: 108323"] Three shots @ 100yds can tell you a lot, a little, or they can tell you nearly nothing. For a hunting application three shot groups can tell you about where your zero is and what kind of distribution (grouping/point of impact you might expect with factory ammunition or a known good reload. But it does little to verify longer range performance and trajectory. For load development they can be useful in such methods as Newberry's OCW method where a group of two or three 3-shot groups have similar points of impact indicate a load insensitive to large POI shift for small charge increments. Three shots at 100yds with a good known load by a top level benchrech or F Class shooter can probably tell you what the rifle/ammo is capable of. Probably not for the other 95% of us. Three shots over a chronograph. Is average velocity around 2800 fps or 2900 fps. Probably doable. Is the average 2900 or 2920? Probably not. Is the 5 standard deviation of one group really better than another with a 10 SD? Don't bet your paycheck or 2 cents on that one. Ultimately what matters is what information you are trying to obtain and understanding what the limitations of are. You can't obtain detailed meaningful statistics from a 3 shot group over a chronograph. You can determine some on target information. You very likely cannot obtain real world group sizes for larger groups than the one that you shot. On target data also must consider the type of firearm that is used. A sporter barrel may put 3 shots touching but throw the next two. It's not designed to be a target rifle but a lightweight, luggable instrument capable of putting two or three rounds into the vital zone of animal. Dispersion at longer distance? Probably a good estimate if you have doped your distances. Meaningful data is inherently related to what you intend to use the rifle for. For a hunting rifle worrying about a 5 shot group can lead you astray since the important shots or usually the first one or two. If shooting F-class or bench rest then it's important to know what the rifle and ammunition do for the course of fire. A three shot group in and of itself probably doesn't mean much. [/QUOTE]
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