I use a Rhino .660 choke and Nitro Company Ammunition (3-1/2") in my SBE II and can consistently put 9 or more pellets in a turkey target vitals at 50 yards. NOTHING patterns better than Nitro 4x5x7 Hevi-Shot with the chokes they recommend. I consistently crumple birds at 40 - 50 yards with Nitro loads (10+ toms dropped with zero cripples). Sure, they're $6.00 a shot, but turkey hunting is a 1-shot deal!
Hevi-Shot's 1-3/4 oz. load, #6 shot, 1090 fps also produces excellent patterns at 40-45 yards (actually better than the 2-1/4 oz load) with my SBE II/Rhino choke. It's a lot easier on the shoulder - I set this load to help a 16-year-old take his first spring bird.
