Milk Jugs at 1000 yards first time.

[LRRPF52]

Barometric pressure, aside from wind, is the biggest factor I look at. Air is less dense the higher you go in altitude. There are less molecules in the same volume of space at higher elevations. This means the bullet has less resistance to its travel, so it flies faster for longer distances, and stays flatter.

It's like a club. Clubs down at sea level are packed, but ones up in the mountains are sparse. It's easier to walk through the mountain club since less patrons are there. This has significant effects on long range shooting.