- Ramped bolt for use with standard AR-15 hammers
- Uses Colt pattern 9mm AR-15 magazines
When modularity, reliability and quality in a 9mm package are all important, the Mk4 is the upper of choice. This 16" upper offers a great way to have fun at the range without spending extra money in ammunition. The Mk4 T is an excellent target rifle equipped with the RKM11 KeyMod free floating hand guard and a nitrided 4140 CrMo steel barrel.