Chrono error???

[howie]

Gents,

Went shooting this afternoon with the fam and a couple buddies. I had worked up three different loads for my heavy barreled AR...69 gr. in front of IMR4064....23.3 grns., 23.7 grns. and 24 grns. Three different loads to see which worked the best for long range. We forgot to set the chronograph up for the first 5 shots with the 24 grn load, and they grouped right at an inch. Set the chrono up and shot the 23.7 grn load next, and the group was a little wider, but the velocities were absolutely nuts!!! They ranged right around 4800 fps! I didn't believe it, thought the chrono had to be off. My buddy reset it and we tried the 23.3 load. The muzzle velocities were right around 2700. After we were done I checked my brass, and there were two that had very slight case neck splits, and very slight flattened primers, but I don't know which loads they were from. Could have been from the 24 grain loads, but maybe not. I don't see any way possible a .3 grain increase could up velocities 2000 fps. I can't make sense of it, had to be a bad reading, right?

[tljames]

Howie couple chrono issues I've experienced are, "low battery" It'll give some bizarre readings and here's a biggie.

Cloudy day and you still have the diffusers on. This one is the tricky one. When is there enough light when is there too much? My experience is if you have a cloudy / overcast day and your readings are wayyyyy out of the norm remove the diffusers and try again. Yet normally if you can see the sun at all you need leave them in place. The Hoser

[howie]

Don't know what kind of shape the batteries were in, it was sunny. Thanks for the response....any way a .3 grain difference in the load could boost velocity by 2000 fps?