Re: pinned barrels and counter-bored charge holes, the change started in 1980 with the introduction of the L frame. Those never had the two notable features. P&R hung around on the K & N frames for two more years, and were phased out in 1982. Same for pinned barrels on the J frames (no "R" in that frame size).

So, the 1980 date corresponds to the disappearance of P&R - or the start of it. That was one factor in the decision to make the break at that point. At least, that is what Lee told me when I asked him about it privately, a short time I joined this Forum.

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Jack
SWCA #2475, SWHF #318