The hole is really the least of S&W problems.
I advise you get up-to-speed on their revolvers or there is a very high probability -- approaching certainty -- that you will buy a piece of junk.
I estimate that more than half the guns leaving the factory have major defects.
The good news is that S&W will fix most of them, at least half of them, if you send it back multiple times.
Ideally, you find one that isn't screwed up to begin with.
This guide is a good place to start:
revolver_checkout.pdf - Google Drive
At a bare minimum, I would have a few tools to check it out: Feeler gauges to check the b/c gap, a no-go gauge to check headspace (can also be done with an empty case and feeler gauges, and a precision-ground range rod. There is a good chance that the barrel was crushed when S&W screwed it into the frame.
It may be more my opinion than anything, but the 637 is one of their worst models to begin with. It's an aluminum frame that isn't durable. It's too small to get a good grip on, and the trigger is terrible -- it may be smooth with a crisp sear break, but it's heavy and has a big pressure spike before it moves back more and then breaks. The K, L, N frame triggers are the best, of any revolver. If you really want a small revolver, get a 2.75" model 66 -- twice the gun the 637 is. But still, be prepared for major problems, because of the kind of quality S&W produces. Great designs. Great technology. Often bad execution. The only good news is they can be fixed with lots of work and often some money.
