Smaller shot? I dunno. Maybe 50 yards, but that might be stretching it. If as far as 75 yards was likely, I'd go ahead to 0 or 00 buckshot
Actually, if 75 yards was likely, I'd recommend a rifle. We've tried the larger buckshot for long shots and the trouble is that there just isn't enough pellets to score many (if any) hits on the skinny little body that lives inside that big fluffy coyote pelt.
I'm not sure, but I think that 00 buck has about 12 pellets in a 12 gauge. There is a lot of empty space between those pellets by the time they get 50 yds out. Back before I was as law abiding as I am now, I tried 00 buck for far out geese and the success was --- not so much. jd