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Posted: 1/23/2010 7:15:56 PM EDT
| I need to test some loads and was wondering how far in front of the barrel/break I need to set up my chrony. I've heard the blast can mess things up and you need to move it farther forward. I usually set it up for everything else about 10 feet in front of the muzzle. I hate to waste ammo trying to get it set up right. |
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Quoted:
I need to test some loads and was wondering how far in front of the barrel/break I need to set up my chrony. I've heard the blast can mess things up and you need to move it farther forward. I usually set it up for everything else about 10 feet in front of the muzzle. I hate to waste ammo trying to get it set up right. I've found that it works well at about 10-15 YARDS. I've also found that when chronographing 50 BMG rounds with a "Shooting Chrony", be sure to have the round travel in the top 1/3 of the window...shoot your rounds low in the screens and you'll get lots of misread rounds. -David Edgewood, NM |
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I have a Beta-Master with the remote readout. I put the chrony out as far as the cable to the remote will allow, that is about 15-17 feet. If you have the remote readout make sure you don't leave it on the bench when you shoot. I found that the concussion off the rifle when fired causes an ERROR reading a lot of the time. I keep my readout under the bench and get a good reading everytime. Another problem I found with mine is if the battery is weak I will get readings that are about 100 fps different than I do with a new battery. So I put a new battery in every spring and get reliable readings.
Ed |
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Quoted:
I place mine at a standard 10 to 15 feet and can not report any issues. Works as intended. I agree with the 10' in front of the muzzle. But like an earlier post, I have to move the remote readout below the bench. Seems that the blast will mess with the electronics / connectors and give me wild readings all over the place. So, I too have moved the main electronics under the bench. Usually no one wants to sit next to me (wonder why, I took a shower?). So I grab the spare stool and move it under my bench with the controller sitting on that. |
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I've put the chrono at least 25yd in front of the brake. You can get false readings any closer.
At Barrett we put a high speed camera at the chrono and you could still see particulates when the chrono when any closer than 25yd. We also saw wildly conlficting readings any closer. As much as 100fps |
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I've put the chrono at least 25yd in front of the brake. You can get false readings any closer. At Barrett we put a high speed camera at the chrono and you could still see particulates when the chrono when any closer than 25yd. We also saw wildly conlficting readings any closer. As much as 100fps Interesting thread. I don't remember every having any significant problems with my chrony placed at 10 to 15 ft. I always seem to get readings consistent with the round used, 2400 to 2800 FPS. Once in a while I'll get an error, but no more often than I do when shooting 5.56 or 7.62. When you mention "particulates" what are you referring to specifically? Dust and dirt kicked up by muzzle blast, or fragments of the solid copper jacket? I shoot a Cobb, which has a huge brake, and I normally shoot from the bench as opposed to being prone on the ground. I can imagine that these factors may have some effect on how much debris may, or may not get blown through the gates? Out of curiosity, how much loss in velocity numbers measured do you see at 25 yrds as compared to 10 ft.? |
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Yes, I agree with last post. No problem once I learned that my 50 just had to much back blast and it was causing the electronics some problems. Once the electronics were put below the bench to shield if from the blast, all is good.
I wonder if this particular particles might be unburnt powder or if it is built up carbon that is being broken off and blown out of the brake forward, and not out of the side. |
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We would see as much as 75-100fps differences between shots in the same grain load. Back the chrono off to 25 m from the muzzle and the deviation dropped to just 5-10fps It makes sense seeing as how there's a packet of material that is moving with the bullet from the muzzle blast that is slowing down more quickly than the bullet. That can throw the timing of the chrony off depending on what it is sensing. I can go up to 50' with my chrony, I'll see if it changes my spread of my loads. |
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With my match load and the chrony set out at 15 feet I get a deviation of 6 fps shooting 5 rounds, are you saying that if I moved my chrony out to 25 yards that the deviation would be less than 6 fps in a 5 shot string. Ed if it is picking up garbage in the air, yes. |
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I do most of my shooting through a chrony off of a concrete bench and a hard surface under it, so there is minimul debris to pick up in the blast. I have shot at some ranges like Alliance where the ground is soft sandy dirt and the blast picks up all kinds of stuff, I could see debris getting thrown out with the blast in that situation. When I shoot prone in the same spot for the weekend match, after the match the ground on either side of the brake is swept down to hard ground and even starts to dig a shallow hole on each side.
Ed |
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