I'll have to find the source of where I read about it. These cartridges 6.5's, 7x57, 30-06, 7.62x54r, 303, 7.7mm, 8x57 which are considering all-around cartridges were designed in a time where no mechanized armies existed. Infantry, calvary, and artillery in long range battle was the way of battle doctrine. Now if I recall, I remember reading about the M88 patrone (the .318" 8x57) having a set of requirements it had to fulfill. One of them was: it was able to reach out at over 1000m and be able to kill a horse. Makes sense that armies needed something cable of killing horse's as that was one of the life line's for logistics or means of mobile attack for every land army of the time. As tactics and war doctrines changed during and after world war two it became evident that these cartridges were over powered and unnecessary in average modern combat engagement and hence the move towards lighter and smaller cartridges. Ie .30 carbine 7.92x33, 7.62x39, 5.56 and etc. This excludes machine gun tactics.