I hate to break it to you all, but when it comes to a .223 marked barrel, you can't go by the barrel marking.
I have a Mark X Mini Mauser factory marked ".223 Rem" but it is a NATO chamber. I understand that Olympic or some other AR maker did the same thing on some rifles.
Even some Colt rifles were marked that way. In some European countries civilians are not allowed to possess military ammo. That's probably why that Mini was marked that way.
my barrel is marked 5.56 nato. works fine with all brass cased ammo. jams with steel cased ammo with the case 2/3 chambered. and i mean jammed. takes a half hour to remove. parts ain't parts. and chambers are not all the same even when marked alike. ymmv
the consolidation of the states into one vast republic, sure to be aggressive abroad and despotic at home, will be the certain precursor of that ruin which has overwhelmed all those that have preceded. Robert E Lee ~Molɔ̀ːn Labé Skýla~
Rumor mill at the local gun shop ( I put very little faith in their knowledge. Almost none, really) is that the Wylde chamber wont handle (cheaper) steel 5.56 ammo well.
Any truth?
My Wylde does not like steel case ammo one bit. It jams up when trying to chamber a round. On the other hand, my 223/556 Bushmaster sucks steel case up and spits it out all day long.
Sure there is a numbers difference between 223 and 5.56 but it doesn't make any real life difference. Completely safe to shoot factory 5.56 in a factory 223 marked barrel. With 10s of thousands of 5.56 and 223 ARs in the USA and with millions of rounds of both ammo flavors flowing freely it is amazing there are not daily kabooms and equally impressive everyone knows not to shoot 5.56 in a 223 chamber.
Any chance you can find some "compelling" evidence on the www that the moon landing was faked, UFOs are real, the govt killed Kennedy, ........?