Simple google search found my answer. Sorry to waste your time.

 

From the web:

In the basement of BATFE Headquarters...............

***Meeting is in Session****

Alright agents, we have a problem. The American shooter is simply too resilient. Gunrunner went tango uniform, so now we need a new plan to undermine the American shooter. How do we do that people?

**crickets**

Come on,someone in this room is awake!

Uh sir, what if we switched the slides?As in , we break into S&W headquarters and swap the stainless slides on M&P's with pot metal ones made from Chernobyl reactor material.With people concealed carrying these days a radioactive handgun would slowly kill anyone who touched it.

**Operation Atom Walker is a Go**

 

Whats the answer? I'm curious.

 

"I'm surprised more of you aren't aware that stainless used in the manufacture of firearms contains a higher content of carbon steel, thus causing it to be magnetic. It is also why this type of stainless WILL rust. Other products which use "pure" stainless are not as susceptible to corrosion, but also tend to be a "softer" metal.

I was going to suggest, but it's already been answered, that Smith figured they didn't have to stamp the name of the material into it since most people could figure that out. It would be like stamping the word rubber on the side of a tire, or stamping the word wood into factory magnas or targets. "

From another forum