If I can kill a turkey with an old 12 gauge A.H. Fox AE loaded with an 1 1/8 oz. of 6 shot; anyone can do it. My Fox is more like full and fuller. I've patterned it at 40 yards and it puts the number of needed pellets to do the job in a 10 inch circle; so, I feel confident a bit past 35 yards but I've never killed a turkey beyond 35 yards.
Take that Sterlingworth out and let it do what it was designed to do.
(dusty 30-30 mentioned Hevi-Shot, it is great stuff but I would never shoot it through a shotgun not rated for steel. Hevi-Shot is hard stuff and not recommended for our vintage guns.)