Jim is right - the S and the N are simply serial number ranges within the N frame revolvers.
Two points for all of us to remember.
In light of the unfortunate American Rifleman article last year, remember that, as Jim says, the S and the N are simply N frame serial number ranges. There is no such thing as an S frame. Therefore, pass on these auction offerings which describe an overpriced 44 Magnum as one of the "rare S frame" 44 Magnums.
Secondly, the only change to barrel installation was that the pin and its corresponding hole were left out. The unfortunate term "crush fit" first appeared, to my recollection, in a magazine article at the time, leading many to believe that the frame and barrel threads were mismatched, or that the threads were cross-threaded or something else, resulting in a barrel that would be securely mounted. This misunderstanding was brought about by the fact that many had assumed that the pin actually held the barrel in place. Apart from the lack of barrel pin and corresponding hole, barrels are installed by the same method as they always have been. There are threads that address the process in greater detail, but essentially, barrels are screwed into the frame until they stop at roughly 10 o'clock on the clock face. They are then turned to the 12 o'clock position with a wrench to a specified torque setting. The resulting friction between the shoulder on the barrel and the frame is where the "crush" is - not the threads. If all goes properly, the sight is straight up and down. One degree past straight up and down and the whole process must begin again by removing enough material to take about one full rotation off the barrel shank, and it all starts again. If any barrel is removed, whether pinned or not, it typically must be re-fit in this manner, as it is almost never properly tight on re-installation. There are threads on changing barrels and it is in an incredibly complex task requiring a very skilled gunsmith and the right tools and gauges.
I am sure the OP and that Jim are well aware of this, but many other readers may not be, and the issue of the pinned barrel comes up almost as often as the issue of +P ammo and whether it is safe to use in this or that model.
