FN makes barrels for the US military, and supplies both M4 and M16 rifles to the military. FN is one of the premier manufacturers of military spec barrels. This barrel is button broached, as is military spec and used by FN, Colt, LMT and other military providers. Featuring the military standard 1:7 twist and chambered in 5.56 NATO, fully chrome-lined and the newer mid-length gas system and M4 feedramps, this barrel is ready for your URGI build or any AR / M4 / M16 style rifle, either as an upgrade or a new build.
FN replacement part number 20-100041
Note: Charlie's also sells the same barrel profile in cold hammer forged barrel: FN 16" mid-length chrome-lined CHF barrel The difference between these two barrels is extremely minor. Typically, the US military uses FN button rifled barrels. The cold hammer forged barrels are sold in commercial markets, and CHF barrels make for very predictable and repeatable production quality. The hammer forge process is different that button rifling, and hammer forged barrels are very capital intensive, and often cost more due to the very expense forge machine. Quality between button rifled barrels and hammer forged, both with chrome lining will be quite similar. They will have equal durability and similar accuracy. Precision barrels with button rifling will tend to be more accurate than a hammer forged barrel, but in a military production environment, we cannot see any difference.