Rem 870 mag, purchased new, 1980. The monster 30" tube was swapped for a 26" after one season. The 26" went after 2-3 for a twenty inch Rem slug bbl w/ rifle sights, and Rem super full choke, the first knurled tube they made.
I have settled on Win 3" 1-5/8 load of #5shot. Basic lead pellets, no space metal. Number #4 shot has always seemed a bit thin in my gun. I shot #6 for quite a few years, usually 2 oz of shot. An article I read a few years back got me doubting #6 lead, past 30 yds or so. I like my shots close of course, but it doesn't always happen, and you can misjudge range sometimes.
My switch to hi-speed #5 lead has been very positive. It seems to hit harder and kill cleaner. Less "floppers" .
Consider some type of sights to improve on the std bead. Pattern whatever you decide.
Be still, he's coming!!!!!!!!!!!!!