I recently had reason to adjust the barrel indexing on an old S&W
revolver I acquired here. Very nice gun!
Anyhow, in the process I discovered that my early edition Kuhnhausen manual was published shortly after the pin was discontinued. A much later edition went into considerable detail regarding specific torque ft/lb values of the various barrel fitting eras.
I found it curious that a need was felt to justify the much greater level of detail and instruction.
Not surprisingly, the old pinned guns needed less torque. (Of course, they weren't chambered for 500 S&W, though!)

At the same time, I dug up an old article by Veral Smith about bore constriction. (Rifle Magazine, 1987) He discusses how torque pressure causes a ripple in the area, which manifests itself as bore constriction. Obviously, the higher the torque, the greater the effect.
He does offer an effective means of correction via handlapping, so it's not all bad news.
His before/after machine rest groups showing the effect on accuracy are eye opening.

Jim