I have a Remington 870 12ga, mod choke, I shoot 2 3/4 inch, no. 3 steel and I bag a lot of birds. I use 4s if I can't get 3s. I have read the data on bismuth and tungsten but I haven't found a reason to spend the extra $ on those loads. The main variable is taking only high-probability shots. With your weapon you should do well with steel if you limit your shots to 30-35 yards max.