Are the parts in a LWRC the same as a standard DI AR (obviously outside of the piston system)? The lowers, triggers, all interchange--in the lower but the upper--where the difference is. Obviously the BCG from a DI to a LWRC is not swappable, that's NOT the question, the question is on the firing pin, and other standard parts, pins, etc in the upper. For instance, could you swap a bolt from one carrier to another? Extractor?