#4 buck is a very different game than BB.

Pellet count on target has to take into account penetration. A lot less pellets of #4 will kill a coyote than BB. I've killed coyotes with ONE 00 buck pellet hitting the vitals, I've rolled coyotes with #5 turkey that would have had 50+ pellets on target at that range, that got up and ran, sometimes anchored by follow up shots, sometimes not. If 00 buck had a higher shot count, that'd be all I'd ever use. #4 buck gives up penetration and KO power, but it has the perfect blend of shot count and power, so THAT is all I ever intend to use (except for when it's hard to find, or I'm just trying other things).

After all of the testing and field experiences I've had killing coyotes with shotguns, it's really too easy to try screwing things up with trying other things. A 22 Hornet will kill a polar bear, a crescent wrench can drive a nail, and goose or turkey shot will kill coyotes, but that doesn't mean any of them are the right tools for the job. If I have access to a 0.660-680" choke and #4 buck, that's what I use. When #4 Buck has gotten scarce, I swap out for a light modified choke with 00 buck. I've never seen any other shot options do better than #4 buck, and none are more prevalent than 00 buck, so without those two, I'd just take a rifle.

I generally live by a 40 by 40 rule of thumb. I won't hunt with anything that doesn't have 40% of the shot on target at 40yrds, it just doesn't get my attention. Essentially, take that to mean that I want 40% of my shot count on target at whatever range I want to kill game, but balanced with the fact that getting much past 40yrds, shot doesn't have the punch - hence, 40% at 40yrds. If a load and choke combination is LESS than that, I never try it afield.

For #4 buck, whether lead or heavier-than-lead, I'm comfortable at any range that patterns consistently with ~15-20 on target at range (give or take 40%). Keeping in mind, the heart of a coyote is only about the size of a small fist. For BB, 40% should be somewhere in the 35-40pellet ballpark.

Double check me on that number, but without looking, I'm thinking that BB is 50 pellets per ounce, but it's been a long time since I did much goose killing, so I might not be right on that. If I AM right, 2oz would be 100pellets, minus 1/8oz, aka ~6 pellets, for 1 7/8oz loads, so 94 pellets, 40% of that is 38 pellets.

I'll admit, I'm still not into copper plated BB shot for coyotes. Even though 38 pellets sounds like a lot, I'm not hugely confident in BB's killing power on coyotes at 40yrds - BB shot doesn't hammer dogs, so it's more likely that you won't get that one shot anchor at 40yrds that you need. So then you're looking at a 45-50yrd second shot, and a 65-70yrd OR MORE 3rd shot on a running coyote, and BB just doesn't have the punch to anchor dogs at those ranges. I killed a bunch of dogs with Winchester Hi-Density loads that are B shot, but heavier-than-lead, and frankly, 40yrds just wasn't a good option even with that. I've killed several with lead BB and some copper plated BB - it's NOT an anchor at 40yrds.

Any shotgun will kill one up close, but at 40yrds, you need an anchor. Even though BB and #4 Buck aren't much different in diameter, it's still a BIG difference. There's 22% more momentum and energy on each #4 buck pellet compared to each BB pellet, so you're talking a BIG difference in penetration and knockdown power.