Yes it's that easy. The lower, upper, bolt, magazine are the same for .223 and 300blk. The only difference in the entire rifle is the barrel. You can take your standard ar lower, slap a 300blk upper on it, and you're ready to go. Provided that you have the ammo. 300blk hasn't really caught on here yet, but it will. It's only a matter of time before more people start getting into it, and availability of ammo becomes better. But for now, if you plan on getting into 300blk, then you should look into reloading. There isn't much ammo for the 300blk available at the moment, it's been sold out for months. Need tips for reloading 300blk, YouTube is your friend.