I had a nice reply all typed out and the forum ate it.
I'll come back later and have another go at it.
Ok, So let's try this again.
I typically use .308 and 7.62x51 (7.62 NATO) interchangeably.
BUT I do not, as a rule, load heavy hunting loads. I do NOT use .308 light magnum loads. Any such loads would be reserved for the .308 bolt action gun and no other IF I were to purchase or load them.
I generally reload ALL my .308 rounds based on data for the M1A/M14 Gas system.
I do NOT as a rule use foreign military surplus. When I have done so I have acquired it through CMP and reports/reviews on the condition and functionality of the ammo are pretty readily available.
My Springfield M1As are cut for a .308 chamber. At least one of them is more or less minimum head spaced or Match chambered. I do not own a weapon that is chambered for 7.62x51 but is also outside of .308 spec.
I had researched this before but with limited success. The Fultan Armory comments I had seen before. I had also seen comments in all the reloading manuals concerning the thickness of commercial vs. military brass. What I've seen in the past with .308 (and .30-06) is that brass from Lake City, Winchester and IMI has all weighed the same and appeared to have the same construction. Federal cases have been the same weight as the others but have had softer heads than the others. (This was some years ago and recent Winchester cases have not had as good reviews as the product did a decade or two ago.) Thus the thickness has generally been the same but commercial case heads tend to get ripped up more quickly in semi auto rifles.
http://www.thegunzone.com/30cal.html (The link from RD above)
http://www.cruffler.com/trivia-June01.html (Link from inside the above article)
http://zediker.com/downloads/14_loading.pdf (Reloading for the Match M14)
From the articles it appears that:
A) The pressure limits for .308 exceed by a fair margin the pressure limits for 7.62 NATO.
B) The chamber sizes for 7.62 NATO are larger than those for .308 Winchester although the cartridge size is exactly the same.
C) While 7.62 NATO ammunition IS standardized there are variations in the application of that standard both in terms of dimensions and pressures. Interchangeability and functionally the same are two different things. While we often see the NATO cross we rarely see the functionality clover.
D) There has been surplus ammunition which has been known to exhibit dangerous overpressures for ANY firearm system.
Thus it appears that with the exception of D) above.
1) 7.62x51 loads are safe to fire in .308 weapon systems.
2) .308 high pressure ammunition may not be safe to fire in 7.62x51 NATO weapons when the NATO chambers exceed the .308 Spec as brass failure may result from the combination of a) stretching b) thinner/weaker brass c) additional pressure (over and above NATO spec.)
3) .308 high pressure ammunition can result in damage to a NATO weapon's gas system
The following happened at a range I've been to and the owner was a fellow I'd shot with at a few range events:
http://www.thegunzone.com/m1akb.html