[activationproducts]

5.56 NATO is not exactly the same as .223 Remington just as 7.62 NATO is not the same as .308 Win. They are often close enough but in match chambers you will notice the difference.

[OldSgt.]

"often close enough but in match chambers you will notice the difference."

I'll give ya that and see ya I don't shoot matched anything. Close tolerances make things jam in real life situations. and that I'm not a long range snipe, generally what works, will work well enough come push up to shove.

[Vic3O3]

IIRC, the differences are in the way the primer is placed in teh cart. base (crimped), and in the thickness of the cartridge with milspec being thicker and thus rendering potentially higher pressures. But as my initial post indicated, I'm not talking about the brass casings here...