I took a HW80 .177 to initiate and set the sights on scope. Sighted in about 6 shots. Take a shot then make an adjustment,then another on and on. I’m sitting on a Stable Table just pumping away, not catching on my cheek position changed dramatically. BKL mounts and they were tight. Guess not tight enough. 95% of the time I use stop pins. Lesson learned. 30-40 rounds. Crow