During the Labor Day sales, Ares Armor had a 16" 308/7.62x51 barrel on sale. There were some questions about the listing because the title listed it as 308 but the barrel is stamped 7.62x51 Nato. Well, for $108 delivered to my door I had to buy it. But it also got me thinking about the possible differences so I did a little research and found an article over at the Fulton Armory website which I will paste a portion of below: "What's the Difference between .308 Winchester & 7.62x51mm NATO?by Clint McKee and Walt Kuleckdumb question i alway thought these 2 ammos where interchangeable but some have told me otherwise whats the story??? jim Hi, Jim, This is a perennial topic, kinda like ".45 vs. 9mm" or "Best Guns & Loads for Deer." They are not the same. They are the same. 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. Best regards, Walt KuleckFulton Armory webmaster" The rest of the article can be found on the Fulton Armory website under the Faq section. So, after reading this, I headed over to Brownell's and picked up a set of Clymer 308 headspace gauges. When I get the barrel delivered I will check the headspace between it and my 308 Aero Precision bolt to report back the findings. Now to wait for the delivery...I hate that part...lol