Catpop, I think the confusion is because you did not state in your OP that you were not crimping into a cannelure, but adjusting the seating depth to fit your gun. Thus the basics for loading revolver rounds, with bullets intended for use in a revolver, do not apply.
The cannelure on any one bullet is determined by the manufacturer. It comes down to the ogive/profile of the bullet, giving enough seated base to give good tension on the bullet and what performed well in test firings. In most cases, exact cannelure position is different amongst manufacturers even with the same weight and same profile bullets. This is why one cannot use given OALs unless the brass is trimmed exactly as the recipe brass an you are using the exact bullet used in the recipe. This is why two different brands of bullets of similar weight and profile may have significant differences in OAL. I load several different brands of jacketed bullets in my revolvers. Generally I buy what has performed well, yet cost the least. Sometimes if one brand is on sale and cheaper than my regular brand I buy them instead. Before I load the new and different bullets, I compare how much base is below the cannelure as this and not OAL determines how much, if any, I adjust my starting load. More base below the cannelure, I start lighter. If same amount of base below cannelure, I'll start with a similar charge. I have yet to ever measure OAL on a revolver round because I always crimp in the cannelure.
