The 7.62 X 51 was the military version that Winchester sold as the .308 to the civilian market when given permission by the military.
The military brass is significantly heavier and better for use in military autoloaders / semi-automatics. The commercial brass may not work work well in such rifles -- says the NRA 'Handloading' book. You will not blow up a rifle, however, by inter-changing the two. Semi-automatics might also require small-base sizing dies to chamber rounds properly.
The use of CAVIM ammo' from Venezuela is a mistake I made one time since their quality control is poor: weak brass, excess pressures, etc. from what I saw in my .308 -- causing the bolt to lock up. :eek: South African and Hertenberger are great in my rifle.
SS'