Delta Force
Banned
I thought it might be reaching too far to think about how the 6.5mm might inspire a shift towards what we now regard as modern "intermediate" rounds since it looks rather like the proposed .270 or .280 concepts with the right hindsight. Frankly I assume the logistical bias towards commonality between MG and Rifle ammunition derails the idea but the Austrians might not have the same concerns as they seek a qualitative advance in their battle rifle. My notion would be a late Twenties to mid-thirties development towards semi-automatic rifle for the infantry as parallel to the Garand as I can conjure out of plausible "what-if" giving the Wehrmacht this advance earlier than the troublesome Mauser that seems to never quite have filled the role. But might this have butterflied the Sturmgewehr? But then I think most might agree that a good semi-auto rifle available around 1940-ish is better than a full-auto in 1944/1945.
I forgot to put this in the original post, but Mannlicher also seems to have pioneered one of the first intermediate rifle cartridges as well in the 1890s. The conventional bolt action Mannlicher M1893 and Dutch Mannlicher M1895 (also conventional bolt action) were produced to use the 6.5 x 53 mm R Mannlicher cartridge. Countries had been moving towards cartridges firing smaller and lighter bullets traveling at higher velocities since smokeless powder was invented, and a few countries (the Romanians and Dutch, also the United States Navy and Marines with the M1895 Lee Navy rifle chambered in 6 mm Lee Navy, an attempt at an even greater leapfrog) actually did adopt intermediate cartridges.
The United States Navy and Marines switched back to full power cartridges in the 1900s for commonality with the Army (although the Navy and Marines even had machine guns firing 6 mm Lee Navy, so they did have a common small arms caliber) while the Romanians and Dutch switched to a full power cartridge just before/during World War II.