just think about how patently stupid that policy is given the two metals.  The extractor is will do more damage to the brass/steel than the projectile will do to the extractor.  I will post a pic later of 2 bolts, one uses primarily metal and the other only brass (precision rifle with far far few rounds downrange) and you tell me which is which.....or anyone for that matter:)

 

I actually won't buy a ready made rifle from a manufacturer that has that policy because not only does it defy logic and reason but tells me they may be making rifles that are inherently inferior for hard use.

 

lwrc, bcm, colt, dd, pof, noveske do not have this policy last time I checked

My guess you may not find documented at S&W either, I was told that verbally and may have mislead folks with the term "policy". Like anywhere else you could probably call there on Monday and receive an entirely different story.  I’d agree that Kel-Tec isn’t exactly your high-end hardware but my SU16(s) only ate Russian ammo. I’m still new to the AR platform but I used my SU16(s) a whole lot more than the AR clones I own. I've had zero issues with the Russian ammo in the SU16's. IIRC there was NO mention steel or polymer ammo in the Kel-Tec owner’s manual. I had two SU16’s and recently traded one. The one I’d traded-in I’d sent back to Kel-Tec in October 2012 for a stock repair. That’s the one that came back with the footnote on the work order that stated “steel, polymer, and aluminum cased ammunitions are NOT recommended”.  Again it was sent in as a comedic repair but they replaced the chrome lined barrel with a salt bath nitride barrel which Kel-Tec decided to switch too on the SU16 model going forward. Originally the SU16’s came with chrome lined barrels so maybe the SBN barrel had something to do with it ammo footnote, I don’t know. Anyway I took both my SU16’s in to be evaluated for a trade and they offered me the same price for both. I opted to keep the chrome lined gun which was the CA version, the one traded was the A version with the SBN barrel.

My WW runs steel cased all day. So do all my M&P handguns.

^^^^^^