It's All In The Angle Of The Story
From a discussion on Plastic on the possible ban of .50 caliber rifles, someone points out that a shotgun can fire a slug of roughly the same weight as a .50 bullet.

Here is one humorous reply:

I think this whole discussion is a classic tempest/teapot scenario, but given your knowledge of the subject I think you're being a little disingenuous in suggesting that the weight of the slug makes a 12-gauge shotgun comparable to a rifle firing a .50BMG round. There is some difference in muzzle velocity, is there not? And a corresponding difference in the energy of the round? And consequently of effective range?

I'm by no means an authority on firearms or their use, but I would suspect that the best way to kill someone with a shotgun from 1500 meters away would be to convert the range entirely into the vertical axis and drop the weapon on his or her head.