muddocktor
Click on the following link to a recent post of a .357 Magnum from 1953 that has the 6 1/2" barrel. If you look closely at the distance between the front of the extractor rod shroud and the rear of the front sight ramp, you will see it is greater than the same gap on the one pictured here. That's a good thing to look for when trying to decide if a particular gun has one or the other barrel length.
Pre 27 6-1/2" pawn shop ... is it a good find???
I hope this helps.