Where are you in Wyoming that you have non-windy days often enough to insure that you have that day to shoot? How much wind-drift at 800-1000 yards and catch a prairie dog? Not arguing, just throwing out questions... Still a kicker of an idea! I have a pal in Laramie who has some kind of 243Improved. He's using that new IMR4007 and says some wonderful things about it.
That 6.5x47Lupau - is that similar to the 6.5TCU ie 223 necked upto 6.5? I had a couple of contender barrels in that one, a 10 and a 14 for IHMSA production and unlimited class. Took an antelope at a little over 300 yards, and the round was pretty much out of steam. and no, I didn't worry about the wind, though I'm sure it was blowing its normal in Farson that day! LOL
Regards,
Sweetwater