Hi Jason,
7.62x51 and 308 Win ammo is indeed interchangeable and won't pose a safety issue in your rifle. There can be some differences between the various 7.62 and 308 reamers out there, mostly centering on throating differences, neck thickness, that sort of thing. The real question for you is, why? The M80 ball ammo is perfectly safe to shoot in your rifle, but it's still essentially crap ammo, at least by what most of us are used to and have come to expect. The 147-152 grain FMJs loaded in this stuff is basically good for 2.5-3 MOA. Admittedly, some will shoot better than this, but that's a lot-to-lot difference, and there's no guarantee of what you're getting here. If it were M118LR ammo, totally different story, but the M80 is basically minute-of-tin-can plinking stuff, and nothing more.
Do yourself a favor and go for something a bit better than this. Even the American Eagle white box stuff should do better than this, and probably won't cost you that much more. If you're reloading your own, go ahead with the M80, and just pull the bullets. Still have to deal with the crimped in primers, but at least your not wasting time with the FMJs.
Kevin Thomas
Lapua USA