AR-15 sheet metal and tube steel upper receiver

grabcad

this is a simple upper receiver design i came up with, it is made from an inner 1.25" tube steel inside and an outer sheet metal component welded or riveted together to make up an AR-15 upper receiver, this would result in less wear and friction cause by the bolt carrier as well as create some open spaces for dirt, debris, and fouling to get pushed into as opposed to impeding the action when dirty