@Jonaschuzzlewit @GabeLakmann @BroDrillard @brimshae @leespringfield1903 That’s all hypothetical though. Today it seems obvious that AR stuff is interchangeable, but the AR platform was seen as integral for the first few decades it was out. Telling them you wanted additional uppers would probably get you a puzzled glance, just like saying you wanted 3 diff. slides for varied barrel lengths on your 1911. The olds would wonder why you’d rather have half a gun instead of 2 whole guns, particularly when they only really had 2 flavors of rifle.
I love the AR platform, but the modularity we see in it today is more a factor of insane, prodigious production levels and an enthusiastic customer base than the inherent design. Until the late 70’s or so Colt didn’t really touch on just how great the system could be once matured. Once they got cheap enough for the aftermarket to start cutting them up and refining systems, it all took off.