I recently aquired a Mark II ten inch bull target model. The gun shoots about 2 inches high at 25 yards. The adjustable sights will not go low enough to bring to point of impact on target. I've cranked the rear sight as low as it will go, but still the gun shoots high. Is there anything I can do aside from new sights to correct this problem. Gun is dead on at 50 yards but of course most of my shooting is closer than that. Other than replacing the sights or shooting low, are there any other options?