ElmerKeith to be honest I am not sure how they did it but I do know that my 38 Special chambered 681 has a noticeably lower front sight than my buddy's 357 Magnum chambered 681 and 581 and puts my 158 +P loads right on the top of the sight at 25 yards. Since the front sight is machined on the rib on my model somebody had to either machine it to a formula or sight it in.
They must have had it down pat because even the Hydra-Shock 147 +P+ stay less than an inch and a half below the 158s. All well within the 10 on the NRA silhouette target.
Remember these are duty guns not bulls eye guns so any slight offset in windage or elevation will still be well within "minute of Bad Guy". In fact the stainless front sight causes me more windage issues by following the sun than elevation issues. During the course of a few hours on our range the inpacts will start to the left of the center and as the sun moves the impact will move across the center and then to the right a total travel of about 4 inches. All the while the elevation is fairly constant. All still in middle of the bad guy. What more could you ask for in a tough as nails duty gun.
Chip King