I hate to be a debbie downer, but I see no advantage in a 7.62x39 ar15, unless you have a ton of ammo for it already. Maybe a 5.45x39 ar15, because the cost of quality bulk ammo is so low right now. Getting parts for a standard ar15 is a breeze, for one in a caliber other than 5.56/223 could be tough unless you want to order online. Just my opinion on the matter, don't let me stop you from enjoying it anyway.