I'm concerned about this as I just ordered an M&P 40c for a carry gun. This concerns me greatly as I live in hot humid southwest Florida.
I've had some people tell me that the M&P rusting issues were just a small batch that got out a while back and others say it is a common problem and they all rust regardless,is this true?
Now thats the million dollar question, is the M&P subject to a higher incidence of corrosion then what would be considered the norm?
I owned the 9c and it had rust on the slide(breech, and on the slide at the sights)right from the box. This was not an early specimen, it was just over a year ago, further I have heard many other similar accounts of oxidation to the M&P slides.
I have a theory as to why this periodically appears in production, it centers around the application of melonite to the stainless steel slide. Melonite is another name for tenifer, which is the salt bath nitriding hardening process done to Glock's!
I was always under the impression that this process was not transferable to stainless, in fact I know for a certainty that it actually destroys the ability of stainless to be, well stainless! It does so by breaking down the steel and rendering it brittle....Something that doesn't happen with carbon steel.
Yet S&W is obviously having the process applied to the stainless steel slides of their M&P's! At any rate my theory is that there is a "narrow therapeutic window" so to speak, where the process imparts a benefit to the stainless, and if the vendor misses it, you end up with obviously flawed slides....