HSSMITH:
I had thought the same thing, about the K-frame .38's not shooting loose so easily-and, I also had felt that these K-frames did not need the extra strength, that such a gun(Like the Ruger "Six Series' revolvers)had(In spades!)over these revolvers! However, I had to send in my first(Like new) M64 back to S&W to fix a serious end-shake problem since it had shot itself loose, early in it's life, without very many .38 rounds having been shot through this gun! This was disappointing to me(Especially, since this was only a .38 revolver!)! I think that strength does matter(Even for a .38!)because this can even make these revolvers withstand the firings of many .38+P loads(Much longer!)before shooting loose! With the Ruger "Six Series" revolvers, you can shoot any "Sane" loading(In .38 or in their .357 revolvers)without any worry of these guns shooting loose! History has confirmed this fact! But(In theory)I grant that in .38 special(Caliber)strength shouldn't matter on the average(But, it is still nice to have this extra "Reserve" strength, that the Ruger revolvers can offer!)!
And, I have seen many(.357)K-frames in Gun Shops that I had wanted to buy(But, had "Rejected")in view of their having too much end shake(And, these being beautiful(Older)S&W collectible(LNIB)revolvers with still beautiful factory S&W bluing)! I very much like these "Classic" S&W K-frames-but, I still prefer the extra strength that the Rugers have over the K-frames! I have seen some Ruger "Six Series" revolvers, that looked like they had been shot to HELL(But, they still hadn't been shot "Loose"!)! This(To me)is amazing!
I agree, that the trigger on the S&W K-frames, are definately better than on the Ruger "Six Series" revolvers! However, with a proper hammer strut spring(Or, a full trigger spring kit)added to the Ruger's, the trigger greatly improves(Although still not quite up to the level of the(Older)S&W K-frames)but still can be pretty good!