Below is some data I got from my KPY Shotshell Ballistic program. KPY recommends that you need 1.50" of gel penetration to reliably kill ducks and 2.50" of gel penetration to kill big geese. For about 25 years I shot coyotes with copper coated lead BB shot, lead BBB and lead T shot.
I came up with wanting 3.70" of gel penetration to reliably kill or breakdown coyotes after seeing the range lead BB shot gets 3.70" of gel penetration in KPY Shotshell Ballistics.
From what I have seen KPY Shotshell Ballistics is pretty accurate. The pellet counts can be off some because the density or the size of the shot that you have can and will vary some. Even store bought factory loads can vary in shot size but you will never know it unless you take some shells apart and count the pellets and measure the shot.
Steel shot is the worst shot for shooting out of a shotgun. Speeding the steel shot loads up helps some but you are still shooting the lightest shot made so it doesn't help the steel shot loads that much.
1600 fps steel T shot gets 3.70" of gel penetration at 26.2 yards, with 65 pellets in 1-1/4 oz.
1300 fps lead #4 shot gets 3.70" of gel penetration at 8.5 yards, with 204 pellets in 1-1/2 oz.
1300 fps lead BB shot gets 3.70" of gel penetration at 46.2 yards, with 77 pellets in 1-1/2 oz.
1300 fps lead BBB shot gets 3.70" of gel penetration at 55.9 yards, with 65 pellets in 1-1/2 oz.
1300 fps lead T shot gets 3.70" of gel penetration at 65.8 yards, with 56 pellets in 1-1/2 oz.
1300 fps 12g/cc BB shot gets 3.70" of gel penetration at 62.5 yards, with 70 pellets in 1-1/2 oz.
1200 fps TSS #4 shot gets 3.70" of gel penetration at 72.9 yards, with 124 pellets in 1-1/2 oz.
It's to bad none of the ammo manufacturers will make a lead BBB or Lead T shot load for coyote hunters. I have brought it up to three different ammo manufacturers at the Shot Show and they just don't seem to think coyote hunters need a shot size between lead BB and lead #4 Buck.
Look at the extra penetration yardage lead BBB and lead T shot get over the lead BB shot.
Also look at the penetration yardage the 1600 fps steel T shot gets compared to the much slower 1200 fps TSS #4 shot.