I've seen Savage and Browning rifles have issues with the harder military-style primers on several occasions. I got an entire box of Barnaul .308(7.62) once from a guy with a Browning who said they where all duds. Worked fine in my Norc M305.
If you want to get an answer to the interchangeability of .223 and 5.56x45 NATO you can look up thousands of discussion posts about it with no clear consensus in sight.
The only indisputable fact is that SAAMI, the organization that sets the standards for pretty much all commercial ammo, does not list .223 as being unsafe to fire in a 5.56NATO rifle but does list "5.56mm Military" as being unsafe to fire in a .223 rifle.
Also note that 5.56x45 is the metric designation for .223 and isn't always (but usually is) an indication that it's NATO spec ammo.
The SAAMI document specifies that "5.56mm Military" is unsafe to use in a .223 Remington chamber. It specifies the "Military" part.
There are strong supporters on both sides of the fence who think the other side is totally wrong. It's kind of like religion.
From a legal stand point if they put both .223 and 5.56 on the box the lawyers wouldn't allow it to be unsafe to fire in either of the two. If the box has both designations listed it would have to be safe for either or else it's a lawsuit asking to happen. Ammo for retail sale in Canada has to be approved by the MNR I believe (or is it another department?) so if both designations are on the box, you can fire it in either.
I've read that running even a few bimetal jacketed bullets (thin copper plating on the outside of a mild steel jacket) through a match barrels will screw it up in a hurry but I've never had issues with my regular hunting spec barrels.
