Picked my M&P9 up off the living room table where it has been sitting for a couple of weeks and noticed rust on the left side of the slide near the M&P rollmark. WT* these things are supposedly through hardened stainless, with a hard coating on top of that. Not much excuse for it to be rusting. Low grade chinese stainless steel? How about the LEO who carry these out in the weather. Pretty disappointed to say the least. Guess I'll have to treat it as a blued piece. Another point for the glock.

Being it has a lifetime warranty i'de send it back to S&W.

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How many guns are too many?

It's a bit more than specs but I didn't expect to see any, the guns never been wet. Not bad enough to send it in but geez.

Why was the gun sitting on the living room table for a couple weeks?

House humidity? Still no excuse. I'd send it back, if for no other reason, just to let them know it's happening.

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Firearms and Saltwater Fishing

While stainless can rust, it probably isn't the stainless that is rusting.

Stainless steel sinks shows rust specs often, it's the debris in the small grooves and pits that rust. I'd bet you just didn't clean it well and got some type of rustable material on the gun and that's what you see.

I'll bet it comes right off.

Wasn't anything ferrous on the surface to rust, it came through the finish under magnification. I was able to remove some of it with a brass brush. Anybody who lives in Florida can attest to the humidity levels and the windows have been open to enjoy the cool nights recently, maybe due to a bit condensation but that was pretty fast acting. Not a big deal to me but unexpected. I leave guns out from time to time because I can.

I live in west central Florida and can relate.But,I'de still send it back.

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How many guns are too many?

Cool guy?

I feel your pain! That's why every firearm that comes through my door gets a coat of Ren. Wax right after cleaning.
Why not give S&W a call? The worst you can hear is a giggle and
a "no". I'd think that even with the windows open, the outside air
would be moderated towards normal by the time it got to a firearm.
JMHO, TACC1.

It is stainLESS not stainPROOF steel. It still needs to be protected.

Stainless steel will rust. I have a $500 propeller made specifically for ocean use, on a boat I occasionally do some ocean fishing in, to readily prove the point.

Even just salt air on land that's not too close to the sea, can cause a lot stainless steel to oxidize/rust and electronics to become ruined.

After all I've heard about rusting, I'm keeping a close eye on my M&P and nothing. I carry it under my shirt when I'm not working, in the truck at one job, and on my duty belt in the weather at the other job. Nothing yet.

I looked at a used 40c last month at a dealers-in a glass case. It had rusted on the rear of the slide, up and over the rear sight. M&Ps do rust on the slide for some reason or another, despite the Melonite treatment.

Preaching to the choir when it come to metal corrosion. The area I live in is considered to be one of the most corrosive in the country but I live far enough inland that I don't get the salt exposure here. The stainless prop on my boat rusts a little too but it sees the salt water directly. I repair electronic equipment that sits close enough to the beach to be continually exposed to salt spray 24/7, you want to talk about corrosion, shocking to say the least. Stainless holds up pretty well in that enviroment without any extra protective coatings but there are many different types of stainless steel which have different characteristics and some more rust resistant than others. The fact that S&W rollmarks "Stainless" into the slide with it's only real benefit in that use being rust resistance and to have it rust so easily kinda sucks IMO. If it gets worse I'll give them a call but I'm not going to cry about it, just beware of the fact.

I've seen lots of different stainless pistols develop rust. Never the less, if as you say, the rust is underneath the black finish, I'd send it back.

Mine's been carried against my skin, against a sweaty t-shirt and it has not rusted. I would not expect it to either.

Out
West

You leave the windows open at night and a gun sitting out on your living room table for two weeks?

I think the nice surprise is that it's still there. Then again maybe the only neighbors you have are alligators in the middle of the everglades .

Where my dad lives in Louisiana,he keeps his windows open at night and the doors too.He has a mobile home sitting on his 7-1/2 acres surrounded by corn and soybeans on the other land around him.His nearest neighbor is over a 1/2 mile away.

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How many guns are too many?

I just picked up an M&P 45 that was badly corroded. When I took it home and cleaned it, I ended up having to use 2000 grit sandpaper to get all the rust off. Luckily it was only in the finish. Sent it out for a duracoat job last week, should have it back by next Friday. Truth be told, if it wasn't for the price, I'd have left it right where I found it. It came with 4 mags and even with having the slide shot it was still well under retail. When I get it back I'll post some pics and the Duracoater's info if you want. $75 for the slide + $10 to ship back. The gun cost me $365.00 so it was worth the experiment to me.