[ARCHIVED THREAD] - FN barrel question

Posted: 9/4/2016 10:52:33 PM EDT

Hey guys I recently built a kickass m16a4 clone. FN upper, barrel, and BCG. My question is about my barrel. It's a 20" FN barrel marked "FNMI MP 5.56 NATO 1/7"
And the gas block is marked "U 12" but between the U and 12 there's a circle with an RI inside it.

Anybody know what the fsb markings mean? Also, since it is not F marked, then it's correct for an A4 right?

Thanks for any help