"The Colt Montor was select fire, semi or full auto, as I recall. But a rifle, none the less."
Uhm... No.
It was a lightened version of the Browning Automatic Rifle, which was a rifle... in name only.
The BAR was called a rifle simply because the military didn't know what else to call it.
Plus, they were probably also following the French example of the Chauchat, which the French had classified as a machine rifle, but which we all known was treated like, operated like, and position as a light machine gun in French usage.
When the US made the horrific decision to adopt the Chauchat, it was classified as the Automatic Rifle, Model 1915. The ONLY thing rifle about the Chauchat was the cartridge it fired. It was even less of a rifle than the BAR.
It was never intended to be the primary service arm for every soldier, i.e., it was never intended to be a battle rifle. It was far too expensive and time consuming to make and far too heavy.
In use, it required a two-man squad, the gunner and an ammunition bearer/loader who, oddly enough, WAS armed with a rifle so he could protect the gunner.
The BAR was a first generation squad automatic weapon/light machine gun.
As its direct successor, the Colt Monitor also wasn't a rifle for the same reasons noted above.
Nor, as I noted, was it aimed directly at the heart of Winchester's primary market as the Burgess had been.
So, Colt didn't produce a rifle for the civilian market until after World War II.