You're right about AA2520. I didn't work with it a whole lot but I did get a 3 shot group of about 2" with 47.0 grns and a velocity of around 2460. Going to 48.0 grns added very little velocity and opened the group up to around 5".
With Varget, I was getting 2400 fps with 49.0 grns. Accuracy was not bad (3-shot 1.5")and I could probably work with it a little more and tune it in. But I was getting much tighter with a grain less of IMR 4064. It has been a good powder for me in the 358 and BLR with 180-225 grain bullets.
I too have compressed several loads with 358 so I may try out some faster powders I have such as Benchmark, RL-7 or 10x and see how they perform. I also have onhand TAC which has worked well for me in the 35 Rem and 223 Rem so I may tinker with those as well.
