Reflecting on the .311 caliber cartridges, it struck me that the best one is actually the least popular. These cartridges are the 7.62x39mm (i.e. .30 Russian), .303 British, 7.7 Jap, 7.62x54mm. adn the 7.65x53 Argintine.
I think the Argentine is the best. It's a rimless case based on a shortened 30.06 and 7.65 brass is readily obtained from re-formed .30-06's. The 7.65 Argentine is right between the .308 Win and the .30-06. It's kind of an enhanced .308 Win.
Yet, the 7.65 Argentine is the least popular. Kind of an orphan. Obviously the reason is the lack of cheap, 7.65 Arg. mil-surp rifles that propelled the popularity of the other .311" caliber rounds. If you research the 7.65 Arg, it was very widely deployed, being also known as the 7.65 Belgian Mauser and was used by Belgium, Spain, Turkey, Eduador, Peru Columbia , Paraguay, Bolivia, Argentina and probably other countries. It was also a chambering of the famous BAR and other full autos. Now it's almost totally gone. This is really too bad at one level, but perfectly understandable at another level I guess. I guess the last thing the ammo companies need is another chambering in an already too crowded field.
Too bad this orphan had to die while the others are flourishing.