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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
New Oehler 35P, New skyscreen rail, First Test Data
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<blockquote data-quote="Pdvdh" data-source="post: 1172737" data-attributes="member: 4191"><p>Dusting off a 5 1/2 year old Thread and adding some additional input after the additional experiences using my triplicate chronograph.</p><p></p><p>Rehashing for those only reading this last Post, I run three chronographs concurrently, meaning all three chronographs record the velocity for each bullet fired. One chronograph is an Oehler 35P, one an Oehler 33, and one a PACT PC2. There are three skyscreens for the 35P, two for the 33, and two for the Pact PC2. All seven skyscreens are mounted on a single, rigid skyscreen rail. The skyscreen spacing is 6' for both Oehlers, and 4' 8" for the PACT PC2. Photos of the setup, showing all 7 skyscreens mounted on the skyscreen rail, were provided in the first Post.</p><p></p><p>I've been out twice in the past week and shot ~50 rounds of .223 Remington handloads over the chronographs. Bullets were the Hornady 60gr .224 VMax. Here's a comparison of the velocities recorded for the last 40 bullets fired:</p><p></p><p><img src="http://i712.photobucket.com/albums/ww125/pdhorwath/Chronograph%20Data%20Comparison_zpsp4vhowes.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>I've been using this triplicate chronograph setup for over five years now, and have recorded hundreds and hundreds of bullet velocities. The velocities recorded and presented in this spreadsheet are representative of the quality of the data I normally obtain. The maximum difference in bullet velocity recorded between the three chronographs for these 40 bullets was 8fps. The last column is a calculation of the maximum difference in the three velocities recorded, divided by the average of the three velocities for each bullet. I consider this to be equivalent to the "percent error", assuming that the average velocity is as close to the true bullet velocity as I'm ever going to measure. In these 40 shots, the maximum error occurred with the 19th shot fired. The average velocity for shot 19 was 2828.0 fps, with a maximum difference of recorded velocity of 8fps between the three chronographs. The percent error for that bullet was 0.28%. The average percent error for all 40 shots is 0.164%.</p><p></p><p>The only time my chronographs act up with any regularity is in fading light conditions. As the light dims in the evening, the PACT PC2 is always the first chronograph failing to record velocity. The Oehlers will continue to record bullet velocity, and continue to provide very comparable data, after the PACT fails to provide any reading. As light lessens even further, the Oehlers will begin to provide inconsistent velocities. I know it's time to quit when the PACT stops working in fading light. I believe the Oehler skyscreens are better able to signal the computer than the PACT skyscreens in low light conditions, and that's why the Oehlers continue to operate in poorer light. PACT may have improved their skyscreens by now. I have no way of knowing. No way to compare their current skyscreens to my skyscreens.</p><p></p><p>Other than poor/dim/failing light conditions, I obtain very comparable data from all three units. HOWEVER, I do occasionally obtain a bad velocity from any one of the three chronographs, with about equal consistency, without any obvious explanation. Any recorded velocity varying by more than 10-15fps from the other two is suspect. Ken Oehler states that every chronograph can and will sporadically produce bad data, and my experience confirms his statement. The only way to recognize faulty data is to have a second instrument recording the same bullet. The bullet speed is the same over all the skyscreens, so if one unit records a velocity significantly different than the others, that confirms it puked out a bad velocity. That's why the Oehler 35P has a proof channel which provides a 2nd, separately recorded velocity for each bullet fired. It's their effort to allow the user to identify bad/faulty data. With my triplicate setup, I receive 4 recorded velocities for each bullet fired. Two from the Oehler 35P and one from each of the other two chronographs. I can almost ALWAYS identify bad data from any of the three chronographs, because two will almost always be in agreement. So I reject the bad velocity from the faulty recording, and use the average velocity from the other two functioning chronographs as the "true" bullet velocity.</p><p></p><p>Thought this might be of interest to some of the members... those still using light sensing chronographs...</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 1172737, member: 4191"] Dusting off a 5 1/2 year old Thread and adding some additional input after the additional experiences using my triplicate chronograph. Rehashing for those only reading this last Post, I run three chronographs concurrently, meaning all three chronographs record the velocity for each bullet fired. One chronograph is an Oehler 35P, one an Oehler 33, and one a PACT PC2. There are three skyscreens for the 35P, two for the 33, and two for the Pact PC2. All seven skyscreens are mounted on a single, rigid skyscreen rail. The skyscreen spacing is 6' for both Oehlers, and 4' 8" for the PACT PC2. Photos of the setup, showing all 7 skyscreens mounted on the skyscreen rail, were provided in the first Post. I've been out twice in the past week and shot ~50 rounds of .223 Remington handloads over the chronographs. Bullets were the Hornady 60gr .224 VMax. Here's a comparison of the velocities recorded for the last 40 bullets fired: [IMG]http://i712.photobucket.com/albums/ww125/pdhorwath/Chronograph%20Data%20Comparison_zpsp4vhowes.png[/IMG] I've been using this triplicate chronograph setup for over five years now, and have recorded hundreds and hundreds of bullet velocities. The velocities recorded and presented in this spreadsheet are representative of the quality of the data I normally obtain. The maximum difference in bullet velocity recorded between the three chronographs for these 40 bullets was 8fps. The last column is a calculation of the maximum difference in the three velocities recorded, divided by the average of the three velocities for each bullet. I consider this to be equivalent to the "percent error", assuming that the average velocity is as close to the true bullet velocity as I'm ever going to measure. In these 40 shots, the maximum error occurred with the 19th shot fired. The average velocity for shot 19 was 2828.0 fps, with a maximum difference of recorded velocity of 8fps between the three chronographs. The percent error for that bullet was 0.28%. The average percent error for all 40 shots is 0.164%. The only time my chronographs act up with any regularity is in fading light conditions. As the light dims in the evening, the PACT PC2 is always the first chronograph failing to record velocity. The Oehlers will continue to record bullet velocity, and continue to provide very comparable data, after the PACT fails to provide any reading. As light lessens even further, the Oehlers will begin to provide inconsistent velocities. I know it's time to quit when the PACT stops working in fading light. I believe the Oehler skyscreens are better able to signal the computer than the PACT skyscreens in low light conditions, and that's why the Oehlers continue to operate in poorer light. PACT may have improved their skyscreens by now. I have no way of knowing. No way to compare their current skyscreens to my skyscreens. Other than poor/dim/failing light conditions, I obtain very comparable data from all three units. HOWEVER, I do occasionally obtain a bad velocity from any one of the three chronographs, with about equal consistency, without any obvious explanation. Any recorded velocity varying by more than 10-15fps from the other two is suspect. Ken Oehler states that every chronograph can and will sporadically produce bad data, and my experience confirms his statement. The only way to recognize faulty data is to have a second instrument recording the same bullet. The bullet speed is the same over all the skyscreens, so if one unit records a velocity significantly different than the others, that confirms it puked out a bad velocity. That's why the Oehler 35P has a proof channel which provides a 2nd, separately recorded velocity for each bullet fired. It's their effort to allow the user to identify bad/faulty data. With my triplicate setup, I receive 4 recorded velocities for each bullet fired. Two from the Oehler 35P and one from each of the other two chronographs. I can almost ALWAYS identify bad data from any of the three chronographs, because two will almost always be in agreement. So I reject the bad velocity from the faulty recording, and use the average velocity from the other two functioning chronographs as the "true" bullet velocity. Thought this might be of interest to some of the members... those still using light sensing chronographs... [/QUOTE]
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