Yes, I understand the way shot sizes work. I though the FS Steel used in Black Cloud was a higher density steel - similar to a Winchester HD load. That's why I chose #4, one size smaller than my usual #3s for ducks.Judging by the destructive capacity of the #4 shot, I though I might need to go another size smaller to a #5 or #6. Again, I was basing this estimation thinking FS Steel was higher density, which should allow me to use a smaller shot size and have the same knock down as a larger shot size of regular steel. Thanks for the advice though.