Krusty said:
I say it all the time... "a shotgun kills with pattern, and not with shot size"...
This is true to some degree, however, you must use a shot size that will provide adequate penetration. If you can't penetrate the vitals, it isn't going to work well.
Coyotes have a lot of fur and the small shot size won't penetrate it well, especially at longer ranges.
A shotgun doesn't kill by pattern alone. It kills with a combination of a dense enough pattern of a large enough shot size with enough velocity to penetrate the vitals.
At very close range, velocity and a very dense pattern can compensate for shot size to some degree so small shot size will kill a coyote often enough. As range increases, the smaller shot sizes lose their effectiveness because the pattern opens up some and they lose the velocity they depended on to penetrate.
That's where the larger shot sizes do better. They carry enough energy to still penetrate the vitals further out. Whatever the range is where your pattern with the larger shot size opens up too much is the effective range of your shotgun, up to the range that the shot no longer has enough velocity to penetrate dependably. With the shot sizes available in 20 ga I wouldn't shoot past 30 yards or so on coyotes.
CanineThumper, there will likely be some who argue with what I've said, but if you think about it I think you will know I'm right. You asked for information, so I've explained it the best way I know how. I won't argue the point because it serves no purpose here. Those who decide to hunt coyotes with bird shot will simply have to find out the truth for themselves.
BB sized shot is about as small as I would use for coyotes and such, and I would still prefer buckshot.
Good hunting to you!
DWL