Are you looking for the theoretical maximum distance a given bullet can travel, fired at the optimal angle?
Back in the early 90’s, a forensic scientist was of the belief Billy Dixon’s Adobe Walls shot was impossible, since, he believed, a .50-90 was incapable of traveling that far. He, another fellow, and Shiloh Sharps set out to find out if this assumption was correct. They found out that a .50-90 could travel a little over 3,600 yards, fired at 35°. Bullet was 675 grains, propelled by 90 gr FFg black, at just over 1,200 fps.
Granted, most people (
)aren’t shooting massive cast lead bullets out of their .50s, so we aren’t quite comparing apples to apples - but those tests just go to show how far even old big bore BP rifles can go.
Shotguns, generally speaking, will loose energy a little faster; but they are still capable of going way farther than one might think.
Might not be exactly the information you were looking for, but food for thought anyway