Rick
At one time the US FY started on July 1. At one point, 1976, this was changed to start the FY on 1 October. The avowed purpose was to allow the POTUS and congress to prepare and pass a budget on time. That is working well today? I was working for the government at the time and we had to add a "T Quarter" that covered the period form 1 July to 1 October. I believe that M1903 barrels were marked with the calander year. A barrel manufactured in August 1945 would have been documented as part of the FY 46 FY buy, but the barrel would have been marked 8-45.