OK, I guess I can't get it figured out on my own. I have good data, but can't seem to figure out how to apply it to get consistant results. I am working with a new bullet (Wildcat ULD RBBT .277cal 150grn) and get a variety of results on a calculated B.C. From the data below I have values ranging from .516 to .590 (I think these are all G1 drag models) depending on what program I use, and what "atmospheric" boxes I check. If someone who understands the weather stuff better than me could help me out I would greatly appreciate it. Here is the data. Chronograph was placed at 10ft & 198 yards (195 yards apart) Initial speed average 3095fps. End speed average 2775fps. It was 60-61 degrees, 33% relative humidity, elevation was 3680ft. Noaa reported the barometer at 29.85 or 1011.3mb. The station is at 3398ft elevation.