switch Upper Receiver Assembly

[sw99]

Hi I am new to ARs and was wonder if I could swich my Upper Receiver Assembly of my XM15 E2S M4 Post-Ban Carbine ,with another Receiver Assembly that like the 20in Post Ban Model Upper Receiver ? I would like to buy one somday and awich them back and forth

[imanaknut]

That is affirmative. Any post ban upper will fit any post ban lower. That is the beauty of the AR design. All manufacturers build their ARs to the same mil-spec. About the only odd-ball was Colt, that made different size engagement pins, I believe to prevent pre-ban and post-ban switching. Currently, all current ones are interchangeable. Go for it!