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Reloading
Oehler 35P Questions
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<blockquote data-quote="Pdvdh" data-source="post: 383092" data-attributes="member: 4191"><p>Here's the explanation:</p><p></p><p>The delta of the differences in <u>your first data set</u> is <strong>15</strong>. This is high in my experience. One clue that you may have recorded one or more bad sets of data in this first data set is that the ES off chrono A is 9 fps higher than the ES off chrono B. You either transcribed errant velocities for shot 2 in your first data set, or else the chronographs recorded compromised data on the 2nd shot in this data set. I would reject the 2711 fps data from both chrono A and chrono B and not include them in any analysis of this first data set. The delta of the differences of the remaining four shots (shots 1, and shots 3-5) is <strong>3</strong>. A delta of 3 demonstrates very good correlation of recorded velocity for the other four shots. Collecting the dual set of data using your proof channel quickly allowed identification of bogus data for shot 2. All the other shots fired over the dual channels of your chronograph recorded a velocity difference of from 10 to 15 fps. When you see a 0 fps difference on shot two, it's apparent that one or both channels of your chrono burped out bad data. The difference in ES will always be less than or equal to the delta of the differences in velocities.</p><p></p><p>The delta of the differences in <u>your second data set</u> is <strong>4</strong>. This demonstrates good, reliable chronograph operation and valid data. Take notice that the difference between the ES from chrono A and chrono B is 2 fps versus the delta of 4. The difference in ES between the two chronos/channels has to be less than (or worst case equal to) the delta of the differences between the chrono A/chrono B data sets.</p><p></p><p>I've labeled the first column of recorded velocities A in order to define that data column as belonging to chronograph A or channel A. The second column is labeled B to indicate that this data column came from chronograph B or channel B, for purposes of explaining if "chronograph A" data is consistently 10 to 15fps faster than "chronograph B", then you're golden. If you want to sell your 35P, I'm ready to purchase. </p><p></p><p>There is no way of absolutely knowing which chronograph (A or B) (primary or proof channel) is recording the velocity closest to the exact true velocity of the bullets passing over your skyscreens. If you want to adjust the skyscreen spacing of one set of skyscreens in order to obtain closer matched data sets for each shot, your could do that, but you have no way of knowing whether Chrono A data or Chrono B data is the more accurate data. </p><p></p><p>I would carefully adjust the separation of each set of skyscreens as closely as possible to the setting you've entered into your 35P. I think you said 4' spacing. I don't own a 35P, but if both sets of skyscreens are precisely positioned at a 4' spacing, then after reviewing and validating the quality of the data (in this case tossing out shot 2 in the first data set), I would simply take the average the two velocities for each bullet and accept the average velocity as the best-you-can-do velocity. </p><p></p><p>The advantage of running dual chronographs and collecting two velocities for each shot fired are: 1) identification and rejection of bad data, 2) ES and SD can be determined with a relatively high degree of precision [with about the same precision as the delta of the differences of velocity between the two chronographs - in your case within ~5fps], 3) the average of two velocities is likely to provide a more accurate velocity than a single recorded velocity.</p><p></p><p>If you had 10 sets of Oehler 35Ps and you shot over all 10 concurrently and took the average of those 10 velocities - well that's about the best you could hope for in IDing the true velocity. Unless you shot over 20 sets of 35Ps. Or 30. Or 40. </p><p></p><p>With your 35P, the difference in velocity between chrono A and B is only 10-15 fps anyhow. You could shoot a very, very long distance, before a 10 fps error in MV entered into a ballistics program would be responsible for the missing of a deer-sized game animal because of the bullet going over or under the animal. </p><p></p><p>Like I said, I don't own an Oehler 35P. But 'Jon A' (User Name) owns two sets of 35Ps and he consistently reports a single-digit delta of the differences in velocities recorded on his. I provided the links in a prior post for your use.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 383092, member: 4191"] Here's the explanation: The delta of the differences in [U]your first data set[/U] is [B]15[/B]. This is high in my experience. One clue that you may have recorded one or more bad sets of data in this first data set is that the ES off chrono A is 9 fps higher than the ES off chrono B. You either transcribed errant velocities for shot 2 in your first data set, or else the chronographs recorded compromised data on the 2nd shot in this data set. I would reject the 2711 fps data from both chrono A and chrono B and not include them in any analysis of this first data set. The delta of the differences of the remaining four shots (shots 1, and shots 3-5) is [B]3[/B]. A delta of 3 demonstrates very good correlation of recorded velocity for the other four shots. Collecting the dual set of data using your proof channel quickly allowed identification of bogus data for shot 2. All the other shots fired over the dual channels of your chronograph recorded a velocity difference of from 10 to 15 fps. When you see a 0 fps difference on shot two, it's apparent that one or both channels of your chrono burped out bad data. The difference in ES will always be less than or equal to the delta of the differences in velocities. The delta of the differences in [U]your second data set[/U] is [B]4[/B]. This demonstrates good, reliable chronograph operation and valid data. Take notice that the difference between the ES from chrono A and chrono B is 2 fps versus the delta of 4. The difference in ES between the two chronos/channels has to be less than (or worst case equal to) the delta of the differences between the chrono A/chrono B data sets. I've labeled the first column of recorded velocities A in order to define that data column as belonging to chronograph A or channel A. The second column is labeled B to indicate that this data column came from chronograph B or channel B, for purposes of explaining if "chronograph A" data is consistently 10 to 15fps faster than "chronograph B", then you're golden. If you want to sell your 35P, I'm ready to purchase. There is no way of absolutely knowing which chronograph (A or B) (primary or proof channel) is recording the velocity closest to the exact true velocity of the bullets passing over your skyscreens. If you want to adjust the skyscreen spacing of one set of skyscreens in order to obtain closer matched data sets for each shot, your could do that, but you have no way of knowing whether Chrono A data or Chrono B data is the more accurate data. I would carefully adjust the separation of each set of skyscreens as closely as possible to the setting you've entered into your 35P. I think you said 4' spacing. I don't own a 35P, but if both sets of skyscreens are precisely positioned at a 4' spacing, then after reviewing and validating the quality of the data (in this case tossing out shot 2 in the first data set), I would simply take the average the two velocities for each bullet and accept the average velocity as the best-you-can-do velocity. The advantage of running dual chronographs and collecting two velocities for each shot fired are: 1) identification and rejection of bad data, 2) ES and SD can be determined with a relatively high degree of precision [with about the same precision as the delta of the differences of velocity between the two chronographs - in your case within ~5fps], 3) the average of two velocities is likely to provide a more accurate velocity than a single recorded velocity. If you had 10 sets of Oehler 35Ps and you shot over all 10 concurrently and took the average of those 10 velocities - well that's about the best you could hope for in IDing the true velocity. Unless you shot over 20 sets of 35Ps. Or 30. Or 40. With your 35P, the difference in velocity between chrono A and B is only 10-15 fps anyhow. You could shoot a very, very long distance, before a 10 fps error in MV entered into a ballistics program would be responsible for the missing of a deer-sized game animal because of the bullet going over or under the animal. Like I said, I don't own an Oehler 35P. But 'Jon A' (User Name) owns two sets of 35Ps and he consistently reports a single-digit delta of the differences in velocities recorded on his. I provided the links in a prior post for your use. [/QUOTE]
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