I don't have anything against .300blk, but its a very niche cartridge, and has led to more than a few KB's due to shooter mix up.
If you aren't going to get a can, 5.56 is imho a better option, and even if you are, 5.56 still makes a good case for itself
If you aren't going to get a can, 5.56 is imho a better option, and even if you are, 5.56 still makes a good case for itself