This late in the game I would be finding factory ammo that I can buy a bunch of boxes and go shoot. I am assuming the factory ammo shoots well enough in your rifle already. Unless you have a bunch of time on your hands load development, sighting in, chronographing and getting some distance shooting verification in will be more time than you have to get ready for your September hunt.
I have the time to get ready. Just got the gun have enough factory ammo on hand, but i also have the necessary components to load, just need to make a decision.
In that case working up a load is always part of the fun for a new gun and going on a hunt for me. Either of those Bergers will put down an Elk so figure out which one your gun shoots better and load up a ton of them.