Like the development for most U.S. military arms, the path for the M1903 rifle isn’t so simple. There were several predecessors between it and the Krag–Jørgensen, and even after adoption, the M1903 went through numerous tweaks before arriving at the rifle we know and love today.
One of the most important “tweaks” was to that of its ammunition. Initially chambered in the .30-03 cartridge that borrow heavily from the British .303 round, the rifles suffered from poor trajectory and quickly worn out barrels. However, by using a lighter, spitzer bullet and a cooler burning propellant, a legend was born in the .30-06 cartridge. Battlefields and deer stands were changed forever.