Quote Originally Posted by 86k10 View Post
thanks for your info. do they also mark their barrels? the only marking on the barrel is 1:9. or do you know what companies that might do that. the reason i ask because i dont know the make of my upper.
I believe the correct milspec marking for a 20" A2 style FN barrel is "FNMI MP CB 1:7" To my knowledge FNMI doesn't make non-milspec ANYTHING, and all true FN barrels should have the proper FN markings for M16's and M4's

BTW, if your carrier is a semi-auto spec, then it's also probably not really FN - there might well be other makers out there that use the "F" stamp, and they're not precluded from doing so since they're not part of any military supply chain.