I will take the advice of those that have been doing this longer than me and just try the partitions to start off with.

Some mention "tuning". How do you know what part of the load recipe to change? What should I be looking for?

I more than likely will not be taking a hunting shot longer than 200 yards but I shoot at 300 for the extra practice. I would like to shoot out to 400-600 yards but I am not trying to get to that point before October.

Another dumb question I'm sure but does the brand of brass make a difference? I have a mix of Hornady, Winchester and Federal. Could that be a variable in finding what the gun likes?