with my muzzle loaders for years when water fowling i used bismuth but then it went off the market, now back on but can't afford the stuff. this past year i went to the new, fairly, itx shot, it shot a nice pattern but also expensive but i can't shoot steel in those old barrels. in as much as i have to choose my shots, like under 30 yds. hitting and killing ducks is no problem. shooting ducks and geese with the 28 ga., most of the birds were shot with #6 bismuth and when that went out i figured out how to reload steel so that it was safe to shoot. one problem with the 28 ga. is many loads can't be bought and loading data is sometimes hard to come by. the last several years i have been using steel and again i am shooting #6 shot and am going for speed, energy, and density. the last three geese i shot were with the 410 using #6 steel and really flopped them.
with that gun, you really have to pick your shots, like being close. didn't mean to confuse anyone, i don't use 7.5's on waterfowl as i can't get it but at closes range it would be a killer, lot of the old time writers suggested 7.5's over decoys as it penetrates the feathers better and the density gives a better chance to hit the head and neck. when steel first came out it was hard to kill anything with the stuff, now that they have the speed, energy up, i am finding that the stuff works every bit as good as lead but a little tougher on the teeth. speed kills and that is why i am having such good luck using mostly 7.5 copper in all my game loads, the stuff works, it also covers my butt should a quail get in the way. i sometimes use some of my older 20 ga. sxs's and still mostly use the 7.5's but can't seem to locate any data to get the speed up for the 20 ga. so most of them go out at about 1300 or less. the 28 ga. gives me better kills and have the records over the years to back it up, shoot faster pellets.
cheers