Even though the carcass has rotted away some new members might benefit from watching this horse's petrified bones being whipped again. Since this 5 year old thread was about barrel pins we can leave barrels that fit inside a shroud for another day.

All one piece S&W revolver barrels are and always were installed the same way. No S&W revolver barrels have interference threads. Barrels are screwed in by hand until the barrel shoulder contacts the frame. The barrel shoulder is cut back in a lathe as needed to make the shoulder contact the frame an eighth to a tenth of a revolution before the barrel rib and sight are straight up. To avoid warping the frame gunsmith tools are used to turn the barrel in the last fraction of a revolution.

While a pin was used the barrels were made with a trough cut across the top of the barrel's threads for the pin. Those troughs were generous enough for random barrels to be fitted onto random frames and still allow the pins to freely pass through. Ordinarily the pins only contacted the frame, not the barrel. The pins could only stop gross rotation of a loose barrel. Some S&W revolver barrels can be rotated so far off that the front barrel latch will not engage yet their barrel pin will still pass through the trough.

The barrel pin was non-functional. However, barrel pins were, and apparently remain, a great marketing gimmick. Other wise, there are only two things to know about them. They help to date the age of revolvers and, if you do gunsmithing, you need to remember to drive them out before removing barrels and put them back in afterward.

Five years ago a member asked in this thread if any pinned barrels were canted. While they were pinned they installed slightly canted just as often as they are now. I bought my first S&W with a canted barrel during the mid 1970s. It had an adjustable sight. I moved the windage to compensate then it shot great for all the years I owned it. A revolver's carry up, lack of rotational play and end shake at lock up, cylinder throat diameters and trigger pull are all more important than a slight barrel cant.