Given a projectile with such a rapidly degrading velocity (400 initial, 232 at 100 yards and 8500 feet), G7 BC's work best. I backed into a meaningful BC by using my field drop figures. This screen print shows a comparison between my home elevation of 700 feet vs Wyoming's Big Horn Mountains at 8500 feet. I missed a nice buck at 82 yards last week out there on my first hunt day because I had not yet gotten around to creating this drop chart prior to the hunt. Darn! I corrected my scope mounted drop chart the 2nd day and killed a doe at 72 yards on the 3rd day of the hunt. Interesting that either a 1000 ft elevation change or a 10 degree temperature change results in a 2 inch drop change at 100 yards. That is quite a critical factor in the field. I wish someone had a downrange velocity that we could use to get a more accurate BC? Your mileage may vary.