Interesting article, thanks for posting it.
My reason for not firing steel cases in an AR (borrowed, of course, as mine got lost in a boating accident) is that it is very hard on the extractor. I don’t want to have to buy (a friend) a new extractor just to save a few bucks on ammo and, of course, you don’t want to have it crap out just when you need it to work or you take a dirt nap.
Perhaps, though, the reason it is hard on extractors is the crud build-up?
It might be hard on the extractor. I’ve heard both sides. Probably because the increased friction with the chamber walls due to buildup makes it harder for the extractor to pull the round out.
I just keep an extra extractor handy, which is a good idea no matter what kind of ammo you use. It’s a 10 minute fix and the extractor is cheap. You can get a DPMS extractor for around $13.
As for the hardness of the casing, it is harder than brass, but still very mild steel, and is far less hard than your chamber. If you think about it, people who run steel case exclusively in AK type rifles don’t seem to have a problem with chamber damage. If I had to guess, I’d say that the steel they use in Yugo, Romanian or even Russian AK rifles probably isn’t as high quality as that used in most ARs and many of those rifles digest steel their whole lives without issue. I have an old SKS (borrowed of course) that I’ve run for literally decades on nothing but steel and haven’t noticed any chamber damage.
Yeah, Tula and Wolf are crap ammo...but anything that lets me practice more for less is worth it.