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Old August 14, 2000, 08:33 AM   #1
STEVE M
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Just curious, at what distance does everyone cronograph their rounds? I've always been at 8ft from the muzzle (rifle and pistol). What about everyone else, closer or farther away, same or different for rifle/pistol?

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Old August 14, 2000, 12:07 PM   #2
Bottom Gun
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The instructions for mine say 10 ft minimum. but last time out I was set up at 12 ft because of the terrain and got nothing but error messages. I assumed because the muzzle blast was still too severe at that distance.
The muzzle blast from my first shot took one of the skyscreens off the machine.
Next time out, I'll try it at 20 or 25 ft and see if that helps. If not, maybe I'll have to make a blast shield for it.
Of course my problem might be operator error since I'm relatively new to chronographs.
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Old August 14, 2000, 12:20 PM   #3
Paul B.
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I believe the standard distance for a chronograph is 15 feet. This is what I have always used when clocking loads. I have noticed that sometimes I will get error messages depending on the time of day. At the range I go to, morning shoots usually come out fine, but in the afternoon, readings can get squirrely or just plain error messages. I think it has to do with the angle of the sun, and even skyscreens fail to stop it completely. One of these days, I'm going to make my own design of skyscreen that covers a larger area. Maybe that'l cure the problem.
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Old August 14, 2000, 12:23 PM   #4
Bottom Gun
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Paul B,

Are there times when it might be more advantageous to leave the skyscreens off altogether?
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Old August 14, 2000, 03:17 PM   #5
Monkeyleg
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Bottom gun, the skyscreens are for sunny days. A clear sky doesn't transmit as much light to the sensors as a cloudy sky does. The skyscreens are there to be illuminated by the direct sun.

I keep mine out about 15 feet or so. Any closer and I get error readings from the muzzle blast.

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Old August 14, 2000, 04:07 PM   #6
Bottom Gun
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Ah-Ha! I knew this would be educational.

Will it help to tilt the unit so the skyscreens are directly facing the sun?
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Old August 14, 2000, 07:13 PM   #7
johnwill
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No, the photo sensors are oriented so they have a field of view of the screens. Leave them the way the factory intended for best operation.
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Old August 15, 2000, 06:17 AM   #8
STEVE M
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Do you measure from the first skyscreen or to the middle of the set-up?
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Old August 15, 2000, 04:01 PM   #9
Paul B.
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Bottom gun. I leave the skyscreens off on cloudy days. Even with high thin cloudiness, the chrongraph should work well without screens. The screens are used on bright sunny days to reduce the "glint" from the bullet. I guess it confuses the "eyes" that use the shadow of the bullet or something.

Steve M. If you want the neasurement to be a reading at 15 feet, place the chronograph so that the center, between the two "eyes" is at 15 feet. If it is not that important, place the start screen 15 feet out and let it go at that. I doubt that the velocity will change that much, and some rifles have sufficient muzzle blast that a screen closer than 15 feet will have more error messages than not.
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Old August 15, 2000, 07:47 PM   #10
Bottom Gun
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Paul B,
Thanks for clearing that up for me. That's very helpful and I appreciate it. I've been shooting and reloading for a number of years, but have never had a chronograph until now.

How about another question? Is the height of the bullet path above the "Eyes" critical? I belive my instructions call for the bullet to travel 4 to 8 inches above the unit. Will there be any difference in accuracy if I send one through at 6" above and another at 8" above the unit?
I guess what I'm trying to ask is: Will a tight group through the "eyes" result in a more accurate measurement and does the height of the group matter so long as it's within the specified range?

Thanks in advance,

Ken
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Old August 15, 2000, 09:54 PM   #11
Clark
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One must be far enough away to not get the gasses affecting the measurement.

One must also be close enough so the chrono is not hit by stray bullets.

In my case there often is no such distance
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Old August 16, 2000, 02:03 PM   #12
Paul B.
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Bottom Gun. I don't think the height of the bullet matters much as long as it falls within the parameters of the chronograph. If there was a difference, it would not be sufficient to alter the average velocity anyway. We're probably talking plus or minus 5 to 10 FPS, maybe even less. I've never given it much thought, to be perfectly frank with you. Frankly, I try to keep the bullets going on the higher side of the limits. So if 4 to 8 inches are the parameters, I try to keep them at 8 inches, or close to it.
I've murdered two chronographs already. Well one anyway. The Chrony can be repaired. A .44 Mag put the quietus to my Oehler and a .44 Spl seriously wounded my Shooting Chrony. I don't care how careful you are, it can always happen. The Oehler probably had well over 5,000 rounds of test ammo of all sorts over it, and the chrony just about the same. I guess, for me anyway, a new chronograph every 5 or 6 years is about par for the course. Mine did get used a lot, sometimes two or three times a week.
Stuff happens, no matter how careful you are.
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Old August 16, 2000, 03:02 PM   #13
Bottom Gun
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Paul B,

Shooting Chrony put a little note in with my unit which said that if you do shoot it up, return it to them for repair.
Seems like I read a letter or two in the gun rags where shooters say they sent them back and they were repaired free.
Might pay you to drop them a line.
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Old August 16, 2000, 04:15 PM   #14
Southla1
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I never managed to hit a chrony but I certainly comitted murder of one fine (Well it used to be fine) Focal tripod! The chrony survived just fine........there was not enough of the tripod left to bury! I did have to look around for some of the lil steel rods that hold the skyscreen but they were OK. .44 Magnum wins again!

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[This message has been edited by Southla1 (edited August 16, 2000).]
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Old August 16, 2000, 09:09 PM   #15
WalterGAII
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If you'll replace the steel rods with wooden dowels, you won't cause any damage to the skyscreens or chrony if you happen to hit one or more of the rods.

I found that my Chrony will give false high readings when I don't use the skyscreens on a pretty bright day. I also don't place my chrony as far away as some of you guys. For handgun stuff I set the chrony up four or five feet from the muzzle.

I don't shoot big-bore rifles, but don't have any trouble with .223's or .243's at seven to ten feet.
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Old August 16, 2000, 09:57 PM   #16
JimWolford
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I use a Pact model chrono and put the screens out at the end of the wires <s> which would be about 15 feet I guess.

Couple weeks ago I was testing a 22 Jet revolver and was getting some totally unbelieveable variations- bad enough that I quit for the day.

After getting back to the house, I called the company and discribed my problems, the person on the other end said "I bet it was a beautiful bright sunshiny day, right?" It seems their equipment cant handle too much sunshine.

The suggested cure? turn the screens on their side( facing *away* from the sun ) and shoot "past" it, not "over" it.

Works just fine<G>

Jim

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