Shaman,
I found some more information regarding the adoption of the .30 caliber bullet by the US Military.
In 1888, Lt. Colonel Eduard Rubin, Director of the Thuns Munitions Factory in Switzerland, submitted his magazine rifle and ammunition to the Springfield Armory for testing for possible adoption by the US Military. His cartridge was 7.5mm (.30 cal.). He resubmitted his rifle and ammunition in the official 1892 Trials at the Springfield Armory, where it lost out to the Krag rifle.
In developing the new ammunition for his designs, Rubin was faced with producing jacketed lead bullets to accommodate the higher velocities. Jackets made from iron, steel, copper and various alloys were tested. He worked with 6.5mm (his initial preference) and 7.5mm bullets. He found it was considerably easier to get consistent quality bullets produced in the larger diameter of 7.5mm. Otherwise 6.5mm might have won out. An alloy of copper and zinc, called Tomac, was the best and most cost effective jacket material he found.
I suspect that the Springfield Armory officials were impressed enough with the work of Lt. Col. Rubin, starting 4 years earlier with his presentation in 1888, that they agreed with his conclusion that .30 caliber was a good, practical bore diameter. If 6.5mm had worked out well enough for Rubin, we likely would have wound up with the 264-06, or 26-06, in our Springfield rifles. The Swiss have long had a reputation for technology and precision. For those rifle Loonys that consider .30 caliber to be the "best" rifle caliber, I suggest that they can probably thank the Swiss and Mr. Rubin.
