Shooting Chrony Perplexity


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wrangler5
August 16, 2010, 11:20 PM
Have been using a Shooting Chrony Gamma Master quite contentedly for 5-6 years. Yes, it has a pretty quirky interface, and does not easily download data to a computer (anybody got a serial port on their computer these day?) but I've made it work.

Recently, though, it has been giving wildly inconsistent readings. Sometimes. I've made baffles to clip on the support rods to keep direct sunlight from hitting the sensors and use them religiously. The last time it went quirky I decided it was too much direct sun in general, so I now set up a photo umbrella on a stand next to the unit, to keep direct sun off the whole body of the unit, leaving the skyscreens in full light.

Today, using this setup to check some low to mid range 38 specials (125g plated bullets over Titegroup and AA#2) out of a S&W snub nose, my first string recorded velocities from 86 fps (yes, eighty six) to 731 fps. The 3 lowest velocities recorded were 86, 134 and 156fps. This was with 4.2g of Titegroup. The string with 4.1g of #2 gave a low of 157fps and a high of 695fps, with 6 shots under 300fps. All of the shots in both strings felt reasonably consistent. I simply don't believe ANY of them were going under 300fps.

I changed the battery, just in case, and shot 5 more of the #2 rounds, and got a low of 90fps and a high of 262fps. Again, I just don't believe it.

I don't recall having light problems in years past. Today was a bright clear day, but as I say the unit and its sensors were in shade.

Anybody else have these problems with a Chrony? It's frustrating enough that I'm wondering about getting a different chrono. For example, the CED Millenium 2 unit doesn't have a printer, but downloads to a spreadsheet via USB port. I could live with that, and in many ways it would be more convenient than the Chrony printed tapes I now lay out on a copy machine and copy onto a single page for my notebook (usually 6 strings to a page.) But does the CED have the same sunlight sensitivity that the Shooting Chronys seem to have?

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The Sarge
August 16, 2010, 11:42 PM
When mine did that....in the past...it always was lighting.....well not always....I have also had that issue when one of the lens was dirty or smudged.....
Of course you could always do what I did....just shoot it.....and get a new one....

taliv
August 16, 2010, 11:47 PM
how far away from the muzzle are you placing it?

shoot some factory ammo over it next time as a control group

i have both CED and chrony. never really experienced the problem you describe with either, in any light. i wouldn't say any of them are more or less sensitive to light.

454PB
August 16, 2010, 11:58 PM
I've owned 5 different chronographs over the last 35 years.

Two rules I always follow with optical sensors:

keep the screens as far as possible from the muzzle, muzzle blast will cause false readings. 15' is ideal.

keep the bullet at least 3" over the sensors. I've found that even .22 caliber bullets will trigger the sensors when 5" to 6" above them.

wrangler5
August 17, 2010, 12:08 AM
Thanks for the thoughts. Here is some additional data, per the queries: The screens were about 12 feet in front of the muzzle - this is about where I always have them when I'm doing pistol rounds. The baffles I use to shield the sensors are 3" tall, so the bullets are traveling well above that level. And I don't think I have any factory ammo - can't remember the last time I bought any except for my Makarov, which I didn't have at the range today. (I did have a 22, though - didn't think to try that.)

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