Great Groups crazy chrono numbers

[jimmymac]

SD and ES are white noise at 100 yards IMO.

 

[fkimble@charter.net]

How fat from the muzzle to the first chrono screen? If too close you will get blow by crossing the screen before the bullet, giving you erroneous readings.

Frank

 

[itchyTF]

I've got a CED and a 35P. Every now and then I'd get a mis-read with the CED so I added the infrared LEDs. Haven't had a mis-read since. Haven't gotten around to "upgrading" the 35P yet. I use a sealed 12 volt battery for it.

 

[ckaberna]

I've got a CED and a 35P. Every now and then I'd get a mis-read with the CED so I added the infrared LEDs. Haven't had a mis-read since. Haven't gotten around to "upgrading" the 35P yet. I use a sealed 12 volt battery for it.
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Where do you find these led’s?

 

[ckaberna]

I cannot shoot past 100 yds because that is all the range I belong to has. I ordered an Oehler 35P yesterday.

Please let us know what the 35P tells you

 

[Tokay444]

.45 and .65 inch groups at 100 aren’t really what I would consider good for that cartridge. If they’re on the ends of your extreme spread, I could see the spread being part of the issue.

 

[itchyTF]

Where do you find these led’s?

Online. When I did mine they were available in short strips. Now I can’t find anything shorter then 5 meters. I was considering getting a 5 meter roll to modify a gunsmith’s Oehler and mine. If I do and have any left I’m willing to sell it.

 

[Ned Ludd]

A chronograph is a valuable piece of equipment in the load development process for many of us. However, there are caveats associated with their use. First and foremost, the group sizes we typically use (4-5 shots) are really too small for rigorous statistical analysis. Second, due to a variety of factors, groups at relatively short distances such as 100-200 yd can often be very tight, even with quite large ES/SD values. So we have to take some of the chrono data with a grain of salt.

Nonetheless, ~250 fps ES seems far too large to solely be caused by the load itself. Light-based chronographs can sometimes be sensitive to ambient lighting conditions, i.e. sunny vs cloudy, etc. It is also critical that the bullets all pass through the same spot/region above the detectors to obtain reproducible numbers. The previous suggestions about looking into the specific placement of the chronograph and ensuring the lighting conditions are relatively constant are good ones.