Chrono errors: Sunlight or battery or ?

[jandbn]

A couple days ago, I went and shot some more of my first pour of boolits over the chrono with disappointing results. The boolits where not really the disappointment though. It was with the chrono. I'm not sure if it was sunlight causing the errors/erroneous data or the cold battery. I hadn’t used the chrono in 27 degree weather before but I want to believe a cold battery is causing the errors. The chrono worked just fine the previous time out and velocities were what I had expected then.

The previous time out with the chrono, it was 40 degrees and such a heavy over cast that I didn't even use the diffusers. I know direct sunlight can cause problems, but this time around the sun was on my back and there wasn't a direct beam of light shining into the chrono's sensors. I did however use the diffusers due to a clear blue sky.

The first string out of a 5 1/2" Bisley was 23.5 H110 WLP 255 grain Lee RNFP WCWW sized .4523 with Felix Lube.

Hi Vel: 2506
Low Vel: 876
Ave Vel: 1316
Ext Spread: 1630
Std Dev: 638

1104
986
938
953
2506
993
876
err
err
1133
2359

Even with removing the two high velocities from the string, the velocity is not what I would have expected with H110. However, there was powder residue in the barrel (poor ignition) where as in the past, I haven't seen that with H110 and heavier slugs (280 grain on up). I didn't hear the sharp crack when the rounds were fired. H110 seems better suited for the heavy weights.

The second string was same as above only with 24.5 of H110:

Hi Vel: 2892
Low Vel: 2710
Ave Vel: 2806
Ext Spread: 182
Std Dev: 65

2710
2726
2760
2732
2766
2777
2824
2867
2867
2892
2861
2886

With this string, I did start to hear the sharp crack when firing like I have in the past with the heavy weight boolits.

Shots for both strings were fired starting at about 12:45 and all within about 45 minutes. The targets showed vertical stringing, but I am sure 99% of that was grip. I didn't dress appropriately and my hands were like ice cubes. Burrrrrrrrr!

There wasn't any snow on the ground to reflect light, so just that leaves the chrono itself, a cold battery, or sunlight causing errors. I would sure like to know if anybody else has had weird chrono readings when it is cold. If not, that leaves sunlight or the chrono itself. Not really wanting to call the manufacturer, ProChrono, I figured somebody here may have had similar or the same problems and would chime in.

[fecmech]

Maybe you were too close to the screens and are measuring muzzle blast?? If this is an Oehler 35 did you plug the stop screen into the proof channel plug?? Looks like you're getting about twice the velocity you should be getting in the second string.

[mainiac]

think your problem is the time of the year.Think the sun sits real low up here in the north,and the chrono cant see good.

I use one of them easy-up canopies,and set it up between the chrono and the sun,,ya have to keep the low lying sun off the screens,or the chrono goes crazy.This only bothers me in the winter months,so i think the sun is just to low in the sky.

[jandbn]

fecmech,

Chrono is a ProChrono Digital and was at 10 + feet to the muzzle.


mainiac,

The sun was not shining into the sensors. The sensor ports were all in shadow. But from what I know of chrono's the sun sure could wreak havoc on measurements. That second string was pretty strange in that the velocities were similar and there wasn't a fail to read. As many times as I have used the chrono, I haven't had any err or false velocities.

[olafhardt]

Mine gave me trouble, then I shot it with a 38. Seems better now.

[mpmarty]

Mine works OK except when trying to use it with my buddys .222 Rem. Bullets are too small and I get failures to read the second screen.