www.ballisticproducts.com has great loads for buckshot.
Lawrence used to make copper plated BB's, but I have not seen them for years.
Hornady makes #4 buck shot in 5 lb containers.
Ballistic products also sells:
#4 buck
F Buck
BBB
BB
F buck kills very well, but I never tried the BBB shot. I have killed a lot of coyotes with BB's, but penetration at longer ranges is limited.
You really do not have to shoot a heavy pay load for a very effective coyote load.
I hunted with a guy that shot 24 pelets of #4 Buck(1 1/4 oz), SP wad, 38g of Blue dot in a 12 ga, and it was a very effective killing load at 1300 fps out of a Win AA hull.
I was using my own load of 32 pellets of #4 buck(1 5/8 oz) with a BP gas seal and a BP12 wad with two splits half way down at 1300 fps out of an active hull.
By the time you buy a loader, wads, etc, you are better to use the Premium factory loads of Copper plated buffered #4 Buckshot...unless you just like to tinker like me...I can't leave well enough alone.