I'd try shooting some slugs through your ic choke tube first. I tried a bunch of slugs (Challengers, Rackmasters, Slugger, and a bunch more) I found that I could get 3-4 inch groups at 100 yds using the remington sluggers 3inch. Challengers were pretty good but they came out high at 50 to be 2 inches high at 100. I was using a Benelli SBE II with a bushnell trophy 1.75-4x Shotgun scope.