Wow! I've never seen anything quite like this! According to multiple posters on this very thread, folks who are concerned about the lock are low-lifes, self-proclaimed experts and "no-nothings."
Seems obvious to me that people have had guns lock-up under firing. It's been documented. The probability of it happening does little to quell the fears of those who don't want the lock. Here in Florida we have 14 deaths due to lightning strikes last year. It is highly unlikely, and I haven't seen anyone struck, I don't personally know anyone that's been struck, so I guess it's safe to go run around in a thunderstorm?
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OP, with regards to the 627 pre-lock vs. the current version, I prefer S&Ws without locks. It's not just the lock, but the combination of the lock, the MIM, and the fact that the majority of newer S&Ws I've seen just don't appear to have the same attention to detail & crafstmanship as the pre-lock guns. In my opinion, even the 80s and 90s guns are built with more love than the current run-of-the-mill models.
That said, I just picked up a 627-5; it was built last December. The gun is very impressive. The build quality is on par with that of the older guns I've come to appreciate. I'm hard pressed to find anything on this revolver that doesn't exude quality. I don't like the lock so I will remove it. I was able to bring it home for $1010 out the door.
As a replacement for my Ruger Wiley Crapp, I had been considering a 2.5" pre-lock 686. Around here, as well as gunbroker, those guns are fetching $800. I decided to toss a little more money in and get the new Performance Center gun. To me, the set of features found in this gun are worth the $210 premium over an older, used pre-lock 686 at the $800 mark. I haven't been able to find a decent *new* 686. Every one I've come across has a canted barrel and I think the engraving looks terrible.
The 627 PC snub is really nice. I wouldn't spend double to get the pre-lock version, especially since we're discussing a handgun that's already priced in the 4 digits. Since you're considering the gun, I'll share a little gang of pics...