I had ER Shaw rebarrel one for me, and I absolutely love it. You can use standard load data...+5% or so.....but there is no need to increase the loads....the Ackley is not neccesarilly about more power, and faster isn't always better. I took my Elk this year at 240 yds with a 200 gr Hornady...straight through the heart. I experimented with a lot of heavy bullets....but decided before my hunt to go with 200 gr bullets to get more velocity/less recoil.....It was a good decision, I have meat in the freezer. I will stick with 200's for a hunting bullet for Elk and deer. If I ever get to go for Big Bears or go to Africa, I would consider heavy bullets, but 200's are plenty for anything in Continental USA. IMHO