Well a couple of points. There was NO, repeat, NO confiscation of any rifles of any type in WWII. The government did transfer its rifles from one unit to another as needed, and that included from NG units under state control to regular army units. But they did NOT take any privately owned rifles of any kind from anyone. (Individuals could, and sometimes did, donate rifles to the government; AFAIK, you can donate stuff to the government today if you want.)
Never said they confiscated civilian owned rifles in the U S.
The Government called in 1918 BARs from both federal and state police agencies, refurbed these with some converted to the WW1 standard 1918A2 or issued as is to Special Forces.
The Australians did call in many privately owned Enfield rifles.
And NG troops ariving at Fort Dix had to turn in their 1903 rifles and received M1917 rifles in return. If the word confiscated doesn't fit I can't think of a better term, they were not given a choice in the matter.
AS near as I can tell the US government was not allowing any sales of surplus rifles other than to allied governments or government agencies in the U S at the time Bannermans advertised the Mod 37. The DCM may have continued to obtain rifles but that would not do the local gun shop or mail order houses much good.
The only civilian owned companies building the Springfield during wartime years were not selling them to civilian dealers.
The M1917 rifles were being refurbed and either issued to US troops or sent to allies , not sold in gunshops.
Not every gunowner in the U S belonged to the NRA or even knew the DCM existed.