With lead, I used full choke a lot, even on decoying birds.......then I could kill them at 20 yards or 50+. Once we had to use steel shot, I never used full choke anymore.......especially for the larger steel shot loads. With 3's or smaller you might get by with full choke, but that size shot is too small to shoot at longer ranges where full choke would be needed anyway. With 1's and 2's you'll find that IC and Mod will likely give you tight enough patterns for killing ducks at 50 yards.
I never patterned BB's but I bet IC or Mod will give you very tight patterns with BB's too. That large shot sometimes needs an open choke to keep the shot from getting bounced around trying to exit the choke; sometimes a full choke will give you some weird flyers and holes in your pattern because the shot is getting forced out of the tight choke.... You just need to pattern it to know for sure.
