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Posted: 11/19/2016 8:47:01 PM EDT
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Just purchased a Caldwell Chronograph and took it out to the range today.
Wild readings from 9mm rounds. My 300BLK Subs were clocking in at 926.75FPS and the guys load data I am using has it at 930FPS. Some 120gr supers I loaded are within 20FPS of the published load data I was using. So I feel confident it was reading these loads just fine. Now on to the issue. Tula 115gr 9mm load is clocking in at 2137 FPS with a 8.3SD..... No way it is moving that fast. Handload 147gr berry copper plate comes in at 2189 with 15.5SD. Published data has it around 890FPS Along with 6 other 9mm loads using the same 147gr bullets and a set using 115gr bullets all came in with these very high 2100 or so FPS. After all this nonsense, I tested some 22lr and another few batches of 300blk. Again all these loads were what they should have been. I had good overhead sun, using both shades. I didn't move the chrono at all, didn't turn it of or anything. Moving from the last 300 to the 9mm loads was under a minute. I just cant figure it out. Other than it was specific to 9mm. Anyone have any ideas? |
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Quoted:
How far is the muzzle from the sensors? When my Chrony reads high it's telling me it's too close. As soon as I move it a few feet further away it's fine. I set the chrono about 12 feet +/- from the end of the muzzle. If it was a distance issue, how did the 300 loads read okay? Not by any means saying that it isn't I'm new to this so I'm ignorant and looking for information. How far away do you recommend that I move to? |
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12 feet is fine. try resetting the chrono when it acts up. if that doesn't work change the distance.
on sunny days i'll put cardboard over the screens, and make sure that no direct sunlight is on the sensors. that helps mine quite a bit. chronos are weird. i've chrono'd some 20,000 rounds, and sometimes they do the strangest things. |
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Quoted:
12 feet is fine. try resetting the chrono when it acts up. if that doesn't work change the distance. on sunny days i'll put cardboard over the screens, and make sure that no direct sunlight is on the sensors. that helps mine quite a bit. chronos are weird. i've chrono'd some 20,000 rounds, and sometimes they do the strangest things. Thanks for the tip. Ill try doing some blocking shade around the sensors to keep out direct light. Also read something about using sharpie over the bullets. Ill give that a whirl too. |
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What were you shooting the 9mm out of and what load data are you using? CZ scorpion pistol 7.7" barrel For data Lee and Sierra books. Example 3.5gr Win 231 loaded to the OAL in book should be moving that 147gr at 905FPS I tried it with Winchester mag small pistol and regular small pistol primers. Mag registered at 2218 regular at 2189FPS. The Tula registered at 2137FPS when google results tell me it should be 1150 to 1230FPS I could understand a slight increase in FPS accounting for a longer barrel. But in no way are the numbers realistic. |
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Quoted:
I set the chrono about 12 feet +/- from the end of the muzzle. If it was a distance issue, how did the 300 loads read okay? Not by any means saying that it isn't I'm new to this so I'm ignorant and looking for information. How far away do you recommend that I move to? 300 BLK subs are going to be much lower pressure than 9MM. Less pressure = less gas to mess with the chrono. 10 - 12' seems like it should be okay, it usually is for me (with a different chrono), but apparently you need to back up a little more for yours. |
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It's kind of strange but sometimes the chroney reads the shock wave instead of the bullet.
I would call this a fluke. You may find next time out that it reads just fine. You could try moving it in or out to see if it makes any difference. I'm not familiar with your model but my "Chroney" sometimes I remove the sky screens. Mostly on overcast days. Motor |
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Was not a distance issue at all.
Angle of the sun was the cause. Sun today was near identical to yesterday. For the heck of it I set up the chrono in the exact same place and distance. Again Tula 115 spouts crazy 2100 FPS. Moved back to 21 feet 2593 FPS. So now I was worried... Moved the chrono angle to the sun about 45 deg different. Bang Tula 1273 FPS as it should be. All he other loads I shot today read correctly as well. Still unsure of why the 300BLK loads would register correctly today and yesterday, where the 9mm wouldn't The only speculative answer I can come up with is the shiny 9mm bullets and the 300BLK was powder coated black lead. But either way the issue is fixed. Thank you everyone for your input. |
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I don't even attempt to chrono on a sunny day, I wait until we have overcast then I get more accurate readings, the sun does some real funny things with chrono's Id have to wait a few months for an overcast day. Desert life of 300+ sunshine days per year. But now with a base calibration numbers for 4 different guns and several loads per gun Ill always have something at the range with me that I can verify with before doing any real testing. |
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