ELR (extreme long range) 22LR. For example shooting a 22 rifle at a target 500 yards away. When shooting steel, you shoot and just shy of 4 seconds later you hear the very faint "ding". A gnat can fart near the line of flight and make you miss the target. [grin] Seriously though, you're looking at a flight time of 1.95 seconds and with a sight height of 2 inches, a 3 degree cant will put the round off center by 38.48 inches (3.21 feet). Weather has become another big variable I've had to factor into the calculations.
I've considered buying some weather stations to place at the local range.