Why is steel-cased Russian ammo considered safe and "the norm" with AKs and their variants, but taboo in the AR world? It internal wear THAT different? Just curious.

Yes, I know there are a lot of AR users out there that will use steel-cased ammo, but you know what I mean.

I have no idea why AR shooters dislike steel cased ammunition.
AKs are designed to feed, fire and extract steel cased cartidges.

It could be steel cased ammunition is dirtier, and has less pressure than brass. A steel case doesn't seal up the chamber quite as well as a brass case, and throws back more gun powder residue, and gas.

When shooting steel cased ammo powder residue forms outside the case inside the chamber because the case doesn't expand and form a tight seal in the chamber.  People used to think it was the laquer coating coming off the cases that fouled the chamber.  So what happens is you fire a lot of steel cased rounds and the chamber gets dirty, then if you shoot brass cased ammo that does expand in the chamber it can get stuck.  This really only tends to happen with .223/5.56 cases as they are less tapered than the x39 calibers.  The tapered 7.62x39 and 5.45x39 cases have no problem ejecting from a dirty chamber.  Shooting steel cased ammo is fine in AR's if you don't shoot brass ammo before it is cleaned.

This
Almost of all my blasting/plinking in my ARs is with steel cased.  I shoot too much to use brass.

I run nothing but Russian steel case (Barnaul and GT) through my two 7.62x39 ARs.  They love the stuff, no issues whatsoever.

Com-Block steel cased ammo was specifically designed to work with their firearms, and their firearms were specifically designed to work with their steel cased ammo.
Com-block weapons have more tapered chambers to allow the steel cases to both feed and extract easier.
Steel cases do tend to extract with more difficulty and so the chambers are tapered to increase reliable extraction.
This sacrifices at least some potential accuracy, which they're willing to give up to get more reliable operation.

Most western firearms are designed with absolutely no thought given to use with steel cased ammo.
Western ammunition was expressly designed to be made of brass.  When it's made of steel, some problems may appear.
Most western ammo has straighter case walls, which makes a more potentially accurate round, and still allows reliable feed and extraction with brass cased ammo.
Since the AR-M16 was never designed for use with steel cased ammo, and they use straighter walled chambers for the .223/5.56 round, extraction may be more difficult with steel cased ammo.
It's the difficulty with extraction that may cause damaged extractors.

Steel cases simply don't expand then contract as much as brass cases do, so when a steel cased round is fired, it doesn't contract as much and you may get sticky extraction, which stresses the extractor.

I have personally seen AR's at the range that have consistent issue cycling some steel case. It seems to be depend on the individual rifle. Witnessed a person having trouble with steel case hand a remaining filled mag to another man with an AR, and that rifle cycle the whole mag no issues. Now one mag does not define reliable, but when the other rifle didnt make it 2 shots before a jam its says somthing.

Oh and i do own AR's. I reload so i never much bothered with steel case in them so i have very little 1st hand experience.

You'll also notice that the 5.56/.223 casing has less taper making it more difficult to extract when the chamber gets carbon buildup vs the 7.62x39. I have and shoot a quantity of AR's and AK's using mostly polymer and laquered steel case ammo with perfect results. I know I wouldn't want to own a finicky AR that isn't reliable with steel case because with the high price of copper, steel case may become the future of ammo

Which ARs are not finicky with steel-cased ammo? From prior posts it sounds more like 5.56 round than the rifle itself.

My Stag will run steel case all day long!

I have started to run every 3rd round brass.  My thinking (and may be wrong) is with the expanding brass, maybe it will yank some of that crud out with it.  I have not fired much, but so far I have had no issues.  And that does streach out my brass ammo.

Sir,
Could you explain why tapered cases are less accurate than straight-walled cases?

Go yugo, brass case and killer ammo. and... the cheapest ha