what 'defaris' said in a nutshell, basically,and I may add in the words from Mr Dan Wesson himself in our visit with him in May of 1973, the fact "aside from the tooling.machining ,etc., the metallurgy of stainless alloys at that time was the rate of expansion and contraction of them ,versus carbon steel (4140 chrome-moly, the prefferred gun alloy) the rate of contraction was slower in the stainless, and thus could cause "binding" of the parts when they got too hot, and yes, the police found this to be true with the model 66's.......
the nature of the beast of stainless affected MANY gun companies and forced some out of business......as noted above, like alloys of stainless can 'gall' so had to use 'unlike' ( different) alloys for say a frame and the slide........(Randal and AMT come to mind)
Todays alloys of stainless are engineered to some awesome specs and high pressure stuff way beyond that of the early 'stainless ' steel built guns..........just look at the 460/500 s and the Lady Smith, or J frame 357 magnums snubbies............

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dan
NRA Benefactor,PMA