Comment Re:Why the lower receiver? (Score 1) 528
My understanding is that replacing the barrel is something a gun owner might reasonably need to do occasionally, while the lower receiver is both not particularly failure-prone (not subjected to high stresses when firing), and holds all the other parts of the gun together.
Sort of like defining a car as the frame, despite the engine, drivetrain, and interior components contributing many more of the qualities we consider essential to that particular model of car.