When i was using triple 7, my first shot would be exactly right where i wanted it, the next 2-3 shots would be exactly 3" higher. I blame the powder. I swithed to pyrodex and all 3 shots stay right where i aim.
If you bump your charge up to 80 grains with that 225 "Or 223 platinum" You'd only be 4" low @ 150 if you sight in dead on at 100 yards.

This is the unit i was hunting last year and was ready for a 150-160 yard shot if i needed it,