What upper is needed for 300 Blackout?
What upper is needed for 300 Blackout? 300 Blackout Upper Receiver: Best Carbine Length Upper Receiver. Primary Weapons MK109 Pro Complete Upper Receiver: Best Overall Upper Receiver. Aero Precision M4E1 Assembled Upper Receiver: Best Upper Receiver Pistol Option. Who makes the most accurate 300 Blackout Upper? Aero Precision M4E1 Aero Precision is one of the…