In the above picture the copper coated lead pellets are number 2's, the next size bigger lead pellets are BB's and the biggest lead pellets are "T" shot from BPI.
All of this information is for lead shot.
4's are .129" dia with 135 pellets per ounce
2's are .148" dia with 90 pellets per ounce
BB's are .18" dia with 50 pellets per ounce
"T" are .20 dia with 31 pellets per ounce
Number 4 Buck are .24" dia with 21 pellets per ounce
I have noticed some people don't pay any attention to pellet size or pellet count when they use a shotgun for coyotes. A real eye opener is to put some different sizes of pellets like 2's, BB's, "T" and number 4 Buckshot in your hand.
Number 2 bird shot pellets are really big pellets when you compare them to 6's or 7-1/2's. But 2's look pretty small when you compare them to BB's, "T" or number 4 buckshot.
On each size difference between 2"s, BB, "T" and Number 4 buck, the pellet weight increase is about 40% more per pellet as you go up in pellet size.
The difference in inches in diameter does not look like much between the pellet sizes but the actual pellet weight per pellet is huge.
Many years ago I shot some coyotes with copper coated lead number 2's and if the shot angle was not perfect, I didn't like the results.
When I switched to copper coated lead BB's I could see the difference in performance right away. At the time I didn't really know that the BB's weighed 40% more than the 2's, but I did see that they performed much better than the 2's.
To get killing penetration on a coyote when the shot angle is not perfect it has to be a heavy pellet. 2's, 4's and smaller size pellets will not penetrate deep enough or break bones like the bigger pellets do.
The point I am trying to make is go with the biggest pellet size in lead pellets that you can and still get a dense pattern. In factory ammo that would be BB's or number 4 buckshot.
It is too bad nobody makes a factory lead load in BBB or "T" shot. I have reloaded BBB and "T" lead shot that I got from BPI. These two sizes seem to be perfect for penetration and pellet count in lead pellets.
The heavier than lead, Hevi-Shot Dead Coyote "T" and the Remington Wingmaster HD Predator "T" and the Rem HD Waterfowl BB loads are even better but they are much higher priced.