Indeed Wonky is the man for technical aspects of match rifles, and the only man I would use for repairs.

Does the device make any difference? I don't know on a 603, but it certainly does on a 700, although as Wonky says you have to be very good to notice the difference, and it takes care and feel to set them up precisely, and when you check them its surprising the number of 700's that are not set up correctly.

Have Fun
Robin