They are not the same, 'cause the .308 Win was released by Winchester several years before the Army standarized the T64E3 as the 7.62MM. You'll get an endless discussion of pressure specs, endless because SAAMI and the Ordnance Dep't measured pressure in different, unrelateable ways. Howver, the chamber drawings are different.
They are the same, 'cause nobody (and Clint's been looking for many years!) makes 7.62MM ammo that isn't to the .308 "headspace" dimension spec. So 7.62MM ammo fits nicely into .308 chambers, as a rule.
But in some 7.62MM rifles the chambers are long (to the 7.62MM military spec), notably the Navy Garands with 7.62MM barrels. Thus, using commercial ammo in such a rifle is not a good idea; you need stronger brass. Use military ammo or the best commercial only, e.g., Federal Gold Medal Match.
Most of the time it's a distinction without a difference. But if you intend to shoot .308 commercial in a military arm chambered for 7.62MM, first check the headspace with .308 commercial gauges first. You may get a surprise.
Whether you have a NATO chambered barrel (M14/M1 Garand G.I. ".308 Win."/7.62mm NATO barrels all have NATO chambers), or a .308 Winchester chamber, keep the headspace within SAAMI limits (1.630 GO, 1.634 NO GO, 1.638 FIELD REJECT)
andiru, if the military is using a faster powder it very well could spike the pressure earlier and higher but have a lower velocity than if it used slower burning powders. Slower burning powders have a lower peak pressure, but a longer interval of time at that pressure (or close to it) where fast burning powders reach peak quicker and drop back off faster which results in slower bullets. For fast burning powders, it is more of a pressure spike instead of a pressure curve (to an extent.
Well Tex, thats only if the military round uses BLC2. I can't say either way
scythefwd said:candiru, if the military is using a faster powder it very well could spike the pressure earlier and higher but have a lower velocity than if it used slower burning powders. Slower burning powders have a lower peak pressure, but a longer interval of time at that pressure (or close to it) where fast burning powders reach peak quicker and drop back off faster which results in slower bullets. For fast burning powders, it is more of a pressure spike instead of a pressure curve (to an extent.
TexasRifleman said:BL(C) in Hodgdon's loading data shows 50,000 psi with a 150gr FMJ, at roughly the same velocity as the NATO load.
So, if BLC2 was developed for NATO loads, and NATO loads use the same bullet as a .308 load, and the velocities are the same, how can there be a 10-20,000 psi chamber difference?
That's CUP they're using, and 50,000 CUP is about 60,000 PSI.
"Reduce charges developed in commercial cases at least 3 percent when loading military brass." Speer Reloading Manual #14.
I tend to lean toward the latter..
It's BS, size only matters in chamber size.I don't load the military brass any differently and have never experienced any pressure signs.
The same difference as 223/5.56 it's all in your head. If the brass was so much thicker reloaders would have to load them differently than their commercial counterpart. I don't load the military brass any differently and have never experienced any pressure signs.