I've always wondered how a quick-change barrel on a machine gun could possibly work. With regard to the Johnson rifles, however, I was just struck by looking at the photos, both of the issue rifle and the sporter model, at how long the action is. The older Swiss straight-pull Schmidt-Rubins also had very long actions. Do you suppose that was a consideration at the time as far as adopting the gun went? I do understand comments about a rifle not looking military enough (too much like a sporting rifle), yet there were rifles before and after that did have quite a sporting look to them, such as the Krag carbine and even the M1 carbine.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.