The gentleman I shoot with was in a military academy during WW2.  Not one of the service academies - this was teen-aged boys.  In early 1944 they received new in the chest M-1903A3s.  No, he's not confused on the type of arm as he's a collector.

After Dunkirk the bulk of the remaining M-1917s were sent to the Brits.  Between the Brits and the Philippines that consumed most of those.  M-1903s were available but M1 production hadn't hit its stride yet (roughly 350,000 by PH day).  I spoke with a gentleman assigned to Field Artillery.  In training, very early in the war, he trained on M-1917s.  That would be in the very small window between entry in the war and rifle production taking off.

The big difference in WW2 from all others can be summarized as "the M1 carbine."  Production of those started in the summer of '42 and proceeded rapidly.  6 million in no time and they actually tapered off well before the war ended as they had enough arms.  3 million M1 rifles, 6 million M1 carbines, at least 1 million M-1903s and that doesn't count sub-machine guns and the like.

The Krag donations to the Navy run into 1943.  The rifle shortage, which was never major during that war, was long past.

Did older guns soldier on in strange uses and locations?  No doubt.  In the early 1980s I was issued a WW2 paratrooper helmet.  Sometimes stuff just keeps soldiering on if it works.  This doesn't change the fact that the M1 carbines and .30-06 weapons were primary and Krags presented an ammunition problem.

Unlike the CW, SpanAm War, and WW1 they met the needs for small arms early during WW2.  I'd go further and state that they made more than they could possibly use.