Sorry, guys. I started this thread and failed to contribute much.
To update. I've taken the revolver to the range six times since I first posted and I've put an average of about 50 rounds a visit through the barrel. Although I never had any failure to rotate issues, I did have the trigger hang on me twice. Once on the third visit and once on the fifth.
However, yesterday, my sixth visit, a problem with the laser developed. Dang it if the laser didn't go out on me after 15 rounds while I was firing.
I pressed the on/off button and the laser came back on...but, after a cylinder reload, the laser again shut itself off while I was firing and no amount of pushing the button down would make it come back on.
I took the revolver home and got ready to closely inspect the laser...and it came on. Batteries are fine.
I don't know...not my best S&W, or handgun by any manufacturer, that I own.
I guess I could send it back, but they'll likely just send it back without any problems being found or resolved.
Whenever I take it to the range it seems like I'm not shooting for fun, but rather to see if the gun will fail. At 35 to 40 cents a round...forget it.
On the bright side, I picked up another 642 last week. No lock.