Just recently got my hands on a 20 gauge 870 and I am setting it up for a youth hunter to use. I know every gun will be different, but I am hoping someone here can give me a starting point. On hand, I have nickel plated BB, non plated BBB, nickel plated F and 4 buck. For chokes, I have a Kicks Buck Kicker (full constriction) and a Carlson's .575 although I think that second one may be a bit tight for larger sizes.