Mark, no Sir, they are two totally different rounds as pictured here (4th picture down) : - ammoforsale.com/ammo-club/762x51-vs-762x39-whats-the-difference/

Cory and Randi are correct, DO NOT attempt to fire 7.62×39 in a firearm chambered in .308,(or vices versa)the headspacing will not be correct and you run the risk of serious injury and or damage to your firearm. Tula does make economical .308 rounds for target practice. Buds is currently out of stock but of you hit the "notify me when in stock" button you can be alerted when they get a new shipment.
budsgunshop.com/mobile/product/64044/tulammo+tulammo+308+winchester+%28762+nato%29+full+metal+jacket />If your needing ammo right away buds does have a decent selection of in stock .308 ( no steel case unfortunately) but the pmc and legend are both solid choices and those can be found here
budsgunshop.com/mobile/search.php/type/Ammunition/caliber/10000660 />Hope that helps have a good day and stay safe.

Tulammo is garbage anyway. i wouldn't recommend. spend a couple more cents per round and get something better.

7.62x39 is a different cartridge from the 308. The 308 nato designation is 7.62x51.

no you can not use 7.62 X39 ammo in a 7.62X51 , 7.62 NATO/ 308 RIFLE ammoforsale.com/ammo-club/762x51-vs-762x39-whats-the-difference/