About a year ago, I got a brand new 640 Pro: couldn't be happier with it. No lock, tight lock-up, perfect aesthetics, great sights. What's not to like?
The story is interesting too. Three or four years ago, I sent S&W my old model 640 no-dash (maybe 25 years old) with some problems. They charged me to fix it, saying that they were not warranty problems. Got it back and the gun had the same problems. Sent it back again and they decided that the problems were associated with a cracked frame. Although they did not refund the $80 or so and shipping from the first fix, they offered me a new gun (much better!). They offered me a new 640-? with the lock. I had heard about the soon-to-be-released 640 Pro and asked for that. They finally agreed to ship me the nicer gun, mostly because when I sent the 640 no-dash back for the second time, they lost it at the factory for several months (Odd story, but that's what they told me on the phone when I complained that I had never heard from them about my gun). I had to wait a couple of years before the 640 Pro finally went into production (it was announced two years before they actually started to make them) but it was worth the wait!
Anyway, the new gun is just great. I think that some nice person cherry-picked it for me, because of the serial number [some letters) 1111. I could not be happier. There were some initial hiccoughs and then Smith make it right!
