Upper Receiver Assembly, Mk4/AR15, Forward Assist

Whether it's the classic style or forward assist functionality that piques your interest, the Mk4 AR15 upper receiver assembly has been a staple in the CMMGlineup. Available in seven different Cerakote finishes, this mil-spec workhorse has been proven over the years and makes a great base to build your next AR15 upper group.This forged, mil-spec upper receiver no longer features an enlarged ejection port. For pistol-caliber builds, this may or may not result in occasional ejection issues. Please see product 55BA290 for use on pistol-caliber firearms as it does feature an enlarged ejection port specifically for that reason.Lifetime Quality GuaranteeWe aim to please, that's why every CMMG product is backed by our Lifetime Quality Guarantee against material and workmanship defects. Learn More.