Many years ago a friend and I were joined on our shooting with a guy with a Webley Mk 3. Occaisionally he would pull the trigger and get a very low powered shot. Eventually we noticed his loading procedure, on the poor shots he opened the tap, inserted a pellet then cocked the rifle, result a blocked transfer port and not enough air. After we kindly pointed this out and he tried cocking the rifle first we never saw him again!
HTH David