are your rings padded inside of them...if not use electrical tape to line them, also make sure to evenly torque your mounts. Allen screw down types work best. I had issue with rear ring slightly being off due to extra mold material on blade part that attaches to guns dovetail....the scope had tendency to shoot left and be at max adjustment range for windage. This on on my QB36 which is similar to a B40. I find lighter scopes on springers work best. Also note my QB36 shoots better with like 10 ounces of weight in hollowed out area in butt of gun. makes gun more balance with scope on it.