The hype about the catastrophic difference between 308 and 7,62 is much overrated. Many cartridges have two calibre names, one in imperial inches and the other in metric. Ever heard about the catastrophic difference between 223 and 5,56 cartridges? Same issue.

You will be able to determine the commercial ballistics from the manufacturer. I'm not always sure if the ballistics of military stuff is that easily available, they will vary from batch to batch manufactured and accuracy too. Hand loading should allow you to tailor cartridges to your rifle.