Hi I'm new to this forum
but to day we shimmed my SB3 with the max Shim tested it with my Muller UFO choke the gun still shot HIGH about a good 80% above my aim
i will keep on playing with shims but i know of the bolt on the Magazine that needs to be loosened to power the point of Impact but mine won't budge
i heard that it must be heated or torched to loosen it
mine won't budge
look at this video
https://www.youtube.com/watch?v=C_1TbHGkY3M