Even out of a butt cruddy bore my 870 Supermag was putting 190 Hevi 13 #6's in a 10" circle at 40.

I checked the bore and it was actually pretty rough so I did a thorough extended polish on the bore and forcing cone and it looks like a mirror now.
I expect after that treatment the same 2.25oz #6 load should give me well over 200 in that same 10" circle since it was basically doing that dirty and rough to start.

Don't overlook a thorough cleaning followed by polishing that bore, especially the forcing cone area.......it could make a significant difference in the patter density of your combo.