One major reason for the S&W K-frames having a tendency to shoot loose much sooner than any Ruger Six-Series revolvers, is because of the fact that the bearing surface area at the end of the crane barrel, is approximately five times larger than it is on the S&W K-frames! And, this bearing surface area takes a major pounding during firing!
Another reason is that the Ruger Six-Series revolvers, were designed from the ground up to withstand the pounding of the .357 magnum's! However, the S&W K-frames(Although beefed up and heat treated, to enable the occasional shooting of the .357 magnum's)was only mean't to fire mostly, the .38 special round for target practice and therefore, to reserve the .357 magnum loads for business use! There were no such "Usage" clause indicated by Ruger, for their Six-Series revolvers! Again, history has shown(With over one million Six-Series revolvers being sold!)that not much tends to ever go wrong with these revolvers!
HS SMITH:
There is a "Lemon" in every gun manufacturers crop of guns-and, I suspect, that your Six-Series revolver, must have been a lemon- nor, "Representative" of the majority of these guns that were put into service! Maybe yours was just a mis-fitted revolver from the Ruger factory?
Despite the above, you are correct, that for the intended purpose, this extra strength isn't required! Although the trigger can be made pretty good on the Six-Series revolvers, the trigger, is the major advantage of the older S&W K-frame revolvers(And, their classic good looks)! I love both of these manufacturer's guns(But, for different reasons!)and, both of them have advantages and disadvanages over the other! We all have our "Favorites"! Although I have several Ruger Six-Series revolvers, I own more S&W's than I do Ruger's! And, I don't particularly care for the larger and, bulkier GP100(But, that's just me!)because I know that the GP100's are even stronger than the already strong(Older, Six-Series revolvers)! It's best to try them out and just pick the revolver that you might like the best(As they are both excellent guns-and, will last a long time, in normal usage!)?