Can't help you there other than to say I've owned a .223 Mini since 1982 - I've always shot 5.56mm Nato out of it since I never knew there was a difference. I can say I've never had any problems with it.
Have you tried looking online at the Ruger website for manual documentation?
To the naked eye, yes. There are very minor differences in the bullet's dimensions.I thought .223 Remington is exactly 5.56 NATO?
And here's the Tech Note from Armalite to this point:
Tech Note 45: 5.56 NATO vs SAAMI .223 Remington Chambers
IIRC 5.56 is thicker at the neck and creates significantly more chamber pressure.Hmm. The only relevant question IMHO is - can one use these rounds interchangeably, or not?
Seems that technical experts are at odds with each other?
IIRC 5.56 is thicker at the neck and creates significantly more chamber pressure.
I know for a fact that firing a .223 round in a 5.56 weapon has no ill effect. The converse is also true is that firing a 5.56 (repeatedly) will damage the .223 weapon (over time).
What I don’t know (for sure) is whether the Mini 14 is truly a 5.56 weapon.