I haven't noticed any difference. For some reason I seem to hit more birds with bismuth, so that's what I shoot.
I bought 5 boxes of hevi shot one season, and I couldn't hit anything with it. Before that I was shooting Bismuth and I dropped alot of geese. So I switched back to Bismuth.
The only reason I could think of that would make me miss so much is: The weight of hevi shot makes it fly a little slower which means you have to lead more. It sounds like a good excuse! :hammering:
Actually I just looked it up, it's the other way around.
Hevi shot 1575