Now that'd be the way to go if you want a 7.62x39mm AR, get the AR47 lower so you can use cheap, reliable AK mags and drums. I still think the .300Fireball is a better ctg. especially in the accuracy dept. Plus, it's a more efficent ctg. too, 17grs of powder in a .300FB gets you the same Vel. as 25grs would in a 7.62x39mm. .308" bullets are more diverse then .310-.311" bullets so you'll have a broader range of bullet weights to choose from. Really, it's up to you. Get a paper and pen and make up a list of what you'll need for a 7.62 vs a .300FB and look at it logically.