Quoted:
Whats the proper way to break in a brand new barrel... Its chrome Moly, 16"
I agree with the other members here, just shoot it, with all my AR, 6 former and currently 6 all with chromoly chrome lined barrels, 20" and 16" barrels, no special break in required.
After shooting I just lightly clean the bore to remove carbon residue, but I clean my chambers and BCGs real good then lube them.
About 40 years ago when I was starting my AR disease I was over cleaning my bore after every time I went shooting, these days I just use a boresnake to clean my bore but I thoroughly clean my bore every 1K to 2K rounds with the traditional cleaning rod and complete cleaning kit.
For more info on maintenance and cleaning go to the noted forum and read all of the tacked threads there.