No ammo expert here but, the WWI cartridge was the 150gr. cupro-nickel flatbase bullet. The M1icon cartridge was the 172gr. boattail copper jacket modern bullet. The M2 cartridge was a 152gr. flatbase copper jacket bullet. We fought WWII, Korea and Viet Nam with the M2 cartridge. The M1 bullet was developed from Swissicon M1911 ammunition and was developed after WWI. Only the Frenchicon used a boattail round in WWI, no one else did so.