I tend to use Bismuth or "soft" Ballistic Products ITX on pheasants, where necessary, because they don't break teeth like steel, or other really hard shot. But have killed enough roosters with #3 and #4 steel to know it kills really well, even in 20-gauge loads, out to 40 yards or so. Which is about as far as most pheasant hunters kill roosters.....

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck