SS1 is correct and as so is duely awarded an SP
It just takes time, I used to anticipate the shot and both stiffen and close the eyes when I 1st began all those decades ago.
I perseveared and eventually broke the habbit, talk him through through the cycle very slowleya few times and each time he closes his eyes, simply tell him to stop and start again.
Another thing is to let him loose off some shots into soft dirt while keeping him engaged in conversation or you loose of some shots while chatting to him until he begins to relax. Seems he is anticipating the bang? maybe an ear plug