I agree that something was off with the .270, I'm tempted to shoot it again, and give the .222 magnum another try if I get the right weather, but my hands took a pounding in the cold yesterday, and my knuckles are stiff this morning. The more I think about it, the more I think the ice crystals and low angle of the sun might have conspired to confound the chronograph. If the magnum primers made a difference it was with the .30/06 and the .375 Ultra, but even with them, the difference between magnum and standard primer wouldn't have been disastrous on a late winter hunt. But in the case of the .375 Ultra (.378 Weatherby, .416 Rigby .338 Lapua) who would ordinarily try to light up 90+ grs of powder with a standard primer?
Attempting to shoot for accuracy under these conditions would be extremely challenging. The heavy clothing interferes with your LOP and cheek weld, and when wearing a glove light enough to allow you to feel the trigger, you'd loose feeling in it long before 5 rounds were fired. At the start of the test I was single loading the rounds to ensure I wasn't pushing a bullet deeper into the case, by the time I only had the .375 and the .458 left to shoot, I was filling the magazine. Maybe next year I can compare accuracy if I can get one of those fancy Doppler radar chronographs that are supposedly coming on line. Yesterday I'd have been doing well to keep minute of Chevy.
Another issue I hadn't taken into account was the effect of the cold on the chronograph cables. The actual chrongraph and printer were inside the truck, but those long cables were exposed to the cold for nearly 3 hours, and the power source is only a 9 volt battery, which also runs the printer.[/QUOTE
You're having better luck with the chronograph in the cold than I do. I've been shooting all winter,i throw on the Canada goose parka and snowmobile pants and just bare hand the trigger. It's mostly been 20 -30 below when I get out but winter is when I develope most of my loads. An iinteresting one was the .264 with h1000 a couple days ago. I shot groups with 65, 66, 67, 68, 69 and 70 grains and everything was hovering around 1/2" mostly under. Weirdly, all were to the same POI too, which is quite a feat for a 6 grain charge variation. It was close to 30 below but not quite, high twenties.