I just put together a cz-550mag .416 action with an Loather Walther 28" bull barrel and had a Mcmillian A-4 stock fitted to the action. I need load data to start streaching this girl's legs. It has an 1-10 twist and I was wanting to run Sierra's 300 gr bthp. I have rl 25, rl 22, and n165. I am want to run her out to 1500 yds. any sugestions?