It was probably a BS ad. I often see Russian steel cased 62 gr ammo listed as "NATO spec" ammo. There is nothing NATO spec about it, it's just a BS statement attached by the seller to make it appear more desirable. I have never seen any Russian ammo that was close to being NATO spec when it comes to .223. The bullets aren't the same, the cases aren't the same, the powder isn't the same, basically none of it is the same.
To be NATO spec it would have to use certain components, such as the FN SS109 bullet. Many just incorrectly assume that any 62 gr bullet is the same. But the Russian 62 gr bullets use an entirely different construction. They use thicker jackets and are loaded to SAAMI specs instead of military velocities. This ammo isn't even close to being as good as US or Israeli M855 62 gr ammo. But it may do well enough for you if plinking is the only goal. Be careful with some sales people. They will often mislead you badly. Expect the Barnaul to be similar to other Russian ammo such as Wolf, but it might be a bit more accurate and less dirty.
-Charging Handle