Update...
I've shot another 400 rounds of steel with no malfunctions now. Seems it was just a break in issue. I switch back and forth between brass and steel with no problems (there's no valid reason why this should be a problem). I still won't be getting any more steel as it wears barrels faster and I'm fine with spending a little more for more barrel life.
Based on what I've observed, the reason the hotter steel ammo was initially short stroking the gun was that cycling pressure is somehow lower (lower pressure at gas port compared to the powder used in brass cased ammo) and with a brand new gun the higher action resistance (surfaces not worn smooth yet) probably caused short stroking.
The polymer coating doesn't melt at chamber pressures despite the myths and stuck cases happen because steel doesn't expand when fired and so more carbon builds up in the chamber. I don't think the extra chamber fouling has anything to do with my previous short stroking issue because I had only fired a handful of rounds prior to switching to steel and getting malfunctions. Only logical conclusion is that the powder used has a different burn rate that leads to more velocity but lower pressure at the gas port.
How much more barrel life do you think you can get shooting just brass cased ammo?
What's the current price differential between steel cased and brass cased ammo?
Have you compared accuracy between the steel cased ammo and brass 5.56
I just have a hard time thinking its worth the extra money to save extending the later part of your barrel life by a small margin this of course is if you intend to shoot your rifle until it is worn out. If you plan on only useing this rifle a few times a year and want a level of accuracy to be maintained then quality brass match ammo would be best.
A quick look around and it looks like there's about a 14 cent difference between brass and steel, excluding match ammo.
So if you shoot 5k rounds of steel and your barrel is ready to be replaced you would have saved 700$ vs buying brass. Now maybe you can squeeze 8k rounds of brass through your ar before accuracy drops. What are you really saving?
I only have 3 ARs left.
my service rifle which is fed 75gn match ammo and only sees about 400 rnds per yr....I don't get to matches often.
My "varmint" gun which only sees brass reloads because I can reload decent ammo that shoots better than steel for less.
Then there's my regular milspec A2. Unless I put it on a rifle rest its hard to tell any difference in accuracy between wolf/tula/bear and m195 m855 labeled ammo and the less expensive brass.
Have fun and shoot it....what ever it is!