The Franklin Armory BFSIII M4 is an American made AR-15 built on an FAI-15 lower. There is a twist however, these rifles are factory equipped with a Franklin Armory BFSIII binary trigger. The BFSIII is an ATF compliant trigger that fires when you pull and release. With practice this can significantly decrease split times/increase rate of fire. Barrel: 16" LTW - 1:7" Twist Handguard: 15" FST Gas System: Mid-length low-profile Caliber: 5.56x45 NATO / .223 Rem