Ugg. That's not good news. If I can't get it to behave better than that, I'm going to try a Magnetospeed.
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Chronograph Weirdness
- Thread starter catorres1
- Start date
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Ugg. That's not good news. If I can't get it to behave better than that, I'm going to try a Magnetospeed.
Reading this thread maybe explains a few screwy things from my chronograph session last week. My 300 win mag that always shoots an average of 2940 was shooting in the mid 2800's. Then I put my AR15 up and it shot mid 2800's too where it really should have been closer to 3200 or more.
Thanks!
Robert
Thanks!
Robert
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. Here's a photo of the setup, showing all 7 skyscreens mounted on the skyscreen rail.
And a photo looking down the skyscreen rail.
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:
I've been using this triplicate chronograph setup for several years now, and have recorded hundreds of bullet velocities. The velocities 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 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%.
When members post that they've obtained variable, faulty velocities from their light sensing chronographs due to differing lighting conditions, I'm not certain how they're able to reach that conclusion with any confidence.
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.
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.
If variable lighting conditions caused my chronographs to record varying and inaccurate velocity data, I would think that the varying light conditions wouldn't affect all three chronographs equally. As I have stated, I don't commonly or repetitively obtain variable data from the three units under differing lighting conditions. As long as there's sufficient daylight, I typically record data similar to the 40-shot set presented above. I'd like to talk to the Oehler folks and pick their brain on the subject. I haven't been able to identify any problematic patterns associated with operating my triplicate chronographs under variable lighting conditions.
Thought this might be of interest to some of the members... those still using light sensing chronographs...
And a photo looking down the skyscreen rail.
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:
I've been using this triplicate chronograph setup for several years now, and have recorded hundreds of bullet velocities. The velocities 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 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%.
When members post that they've obtained variable, faulty velocities from their light sensing chronographs due to differing lighting conditions, I'm not certain how they're able to reach that conclusion with any confidence.
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.
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.
If variable lighting conditions caused my chronographs to record varying and inaccurate velocity data, I would think that the varying light conditions wouldn't affect all three chronographs equally. As I have stated, I don't commonly or repetitively obtain variable data from the three units under differing lighting conditions. As long as there's sufficient daylight, I typically record data similar to the 40-shot set presented above. I'd like to talk to the Oehler folks and pick their brain on the subject. I haven't been able to identify any problematic patterns associated with operating my triplicate chronographs under variable lighting conditions.
Thought this might be of interest to some of the members... those still using light sensing chronographs...
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I hardly have any issues with my chrono, I get the very very rare ---- I used to use a 22lr to verify now I use my 17hmr to verify. Basically you shoot the rim fire across it before you start the 22 was around 1220 fps from memory, the 17 hmr Winchester will run a bit over 2500 so these rounds are your known quantity. You may occasionally get a slight variance from lot to lot but I found the difference to be insignificant. I always use the sky screens and make sure they're directly over sensor, don't let shadows fall across the sensor. But I hardly do the verifying anymore because I've got a good deal of data plugged into Quick Load with the powders and calibers I mainly use so I know what to be expecting before I even get to the range, chrono proves Quick Load and the more loads I chrono the more accurate QL becomes. The last 7 loads I've tried the worst prediction was still under 20 fps average to a best of within 5 fps average. I usually am also shooting groups at the same time as well and concentrate around the OCW and am very pleased with the results
Okay, so a last update... but first...Phorwraith...that is a seriously sick setup. That's awesome!
Gunner....your idea of using the 22...don't know why I did not think of that....but did that today and it seemed to verify that the Chrono if functioning just fine and the problem was elsewhere.
So I put up a new posting on it because I need some advice. Long and short....it's the loads. I reshot my more recent loads and they were low, but before I went to the range, I found some old stuff that I forgot to shoot and took that to. Bingo...velocities right where they should be.
Saved a few of each batch measured them...OAL the same. Pulled bullets. Powder charges the same.
So have a look at the new post for the rest of the details, there were a few things, but I'll just leave it to one post.
But thanks so much for all of your help and advice!
Gunner....your idea of using the 22...don't know why I did not think of that....but did that today and it seemed to verify that the Chrono if functioning just fine and the problem was elsewhere.
So I put up a new posting on it because I need some advice. Long and short....it's the loads. I reshot my more recent loads and they were low, but before I went to the range, I found some old stuff that I forgot to shoot and took that to. Bingo...velocities right where they should be.
Saved a few of each batch measured them...OAL the same. Pulled bullets. Powder charges the same.
So have a look at the new post for the rest of the details, there were a few things, but I'll just leave it to one post.
But thanks so much for all of your help and advice!
