I shoot mainly IC or LM choke tubes. Briley's with extended knurled grips. I'm a believer in longer tubes. I shoot a Hevi-shot as my first shell, backed up by two Hevi-Steel. I have found this combo to be really effective. The places I hunt are smallish, tidal creeks. So while the water you are hunting can be small, you have to stay back in the tree line to be concealed properly, which can lead to decoying shots at 40 yards. Steel isn't hitting on much at that range. I have found that just the little bit of difference with Hevi-steel makes a huge difference. Do make sure to pattern it though, as I have an 870 with Thin-Wall chokes that won't shoot much of anything other than dove loads and buckshot well.

By the way, I use the #4 Hevi-steel, in 3".