I'm also a brand new 257JDJ owner. The barrel I got came with the loads the previous owner had set up and he recommended W748 with a range of loads that will give MOA with a 100 grain Nosler BT bullet. He also had an AA2520 load that was shooting very well for him with a Hornady 100 grn bullet. I have some H322 sitting around that I want to play with as well, but I haven't yet. Maybe on some of the lighter varmint bullets. I'll let you know what I come up with if I ever try it out.