According to De Haas, Brophy , and Wiki, US Model 1903 production was just over 3 million complete rifles, made by Springfield Armory and Rock Island Arsenal. They only came with 4 groove (6 groove very rare, abt 6,000 made) barrels. No M1903 rifles were made with 2 groove barrels unless arsenal rebarrelled or repaired at a later date. Number of spare parts and spare 4 groove barrels produced must have been astronomical. The Government also bought barrels made by High Standard and Johnson Automatics in the late 1930's-early 40's, and these were 4 groove.
Remington Arms and Smith Corona made 1,415,593 M1903A3 and M1903A4 (A4's were sniper rifles, not that many made). They originally came with 4 groove barrels, but in late 1941-early 1942 production switched to 2 groove barrels. Remington invented button rifling at this time, rifling was broach cut prior to 1941. Total 2 groove Remington production was probably 750,000 complete rifles, and 100,000 extra barrels for parts. Avis Rifle Barrels and Sedgely also supplied barrels to Smith Corona. I would be pretty sure Avis and Sedgely barrels were not 2 groove, that was a Remington process.
When I was young, you could still buy complete rifles($29.95) and spare parts in cosmoline. The supply ran thin in the 1970's.