Quoted:
Guess it doesn't matter much. First time breaking in a simi auto chromed lined and thought I'd check.
Are you
certain the entire bbl is chrome lined & not just the chamber?
Generally speaking, most AR bbl's aren't chrome lined the entire length of the bore but the chamber only in order to help extraction with a filthy rifle. Chrome lining means you will never have a NM spec'd bbl as well as the chrome won't be uniform throughout the bore. (Or so I have been told.)
Now, what *I* do on bbl break-in is shot a single shot, swab the bore out with a wet patch 2-3 times, shoot again, swab again 2-3 times with a fresh, clean wet patch, etc. for about 10-15 rds. Yes, it's boring as hell. However, the times I have done this has seemed to result in a very very finely accurate rifle.
As a counterpoint for those whom say a break-in isn't necessary, I contend it costs virtually nothing but a few extra minutes of my time. An extra accurate bbl is certainly worth my piddling extra 30-45 minutes of time, IMO.
My .o2