Are such loads suited to S&Ws? Would the additional recoil of the heavier load be reasonable in this size gun, or might it be argued the more manageable 255 is worth the less power for the same of quicker follow up shots? Whatever I get, I'll have to practice with it.
Not sure if this still applies today, but some vintages of the 629 had tight cylinder throats. Brian Pearce had a good article covering it, but it is several years old now and I don't know what the current situation is with the latest 629 throats.
I had a 629-6 with 4" barrel, and it did have tight throats so I loaded jacketed bullets. They are supposed to handle the tight throats better than cast bullets. Supposedly they get squeezed in the throat, but then have some "springiness" that allows them to obdurate in the bore of the barrel. Some people claim that cast bullets, once they pass through a tight throat are essentially re-sized (too much) and are not always able to obdurate sufficiently which can affect accuracy and cause leading.
Easy for you to check the throats, once you get the revolver though.
Looking at my old notes, for the 4" 629, I loaded the 240gr XTP quite hot with H110 but much preferred the same bullet at 1100 - 1200 FPS with Universal. Very pleasant to shoot.
I settled on the 300gr XTP at ~1100+ FPS. Moderate recoil and was very accurate. However, I think it was a bit much for the N-frame as it started to loosen up. I don't recall how many rounds I shot, but if I were to do it all over again I would probably keep it at 1000 FPS for the 300gr to help minimize wear and tear.
