I recently bought a 2nd hand S&W 686-6 6 inch revolver and went out to sight it in. Shooting from a rest at 25 feet I zeroed the sights with a resulting 2 inch diameter round grouping using .38 special (standard, not +P) ammo.

I then tried three different brands of .357 Magnum ammo from the rest at the same distance and was surprised to find the grouping was a 4 x 6 inch oval that was 8 to 12 inches to the lower left of where the .38 special grouped.

Is that typical to see that much difference at rest from 25 feet between .38 special and .357 magnum ammo?

I did notice that the barrel clocking was slightly passed TDC and hence needs be be reclocked but what would you expect or have you seen from your 6 inch 357 revolvers?

I appreciate your input.
CAMario