What I am seeing out of my 870's and LB's is that if I don't clean barrel (tico tool) in between shots my patterns drop off big time. That's with kicks chokes 21"bbl, 28"bbl, LB 5's and 6's. After polishing I see that first few patterns drop off but deep cleaning, as long as the barrel is dry they shoot fine. New chokes I see this allot.( patterns improving shot after shot) I run a box of cheap shells through the choke, clean, and then pattern the turkey loads.