Hey Mike, you didn't mention what brand of loose powder you're using, but 70 grains of Triple Seven should be getting you something around 1700 fps with that 200 grain bullet, and 70 grains of Pyrodex RS should be in the 1650 range. Those are killing velocities out to 100 yards easily. So if you've tried many different combos as you've said and can't get decent accuracy with anything over 70 grains don't be afraid to use that load.