155's are good for about what you said. IMO
whats your twist rate?
if you want to jump out to longer ranges, you pretty much have to jump up to 165-175gr.
I like the Berger 168's, though they're a little expensive for finding a good load. So I stick with the BST 168's or the AMAX 168. (the BC is just barely lower on the AMAX -- just enough to make a difference at longer ranges compared to the BST's).
Once you pass 600 yards, every little bit of BC you can get, you better get!! And with the 168's dropping in excess of 300", the 175's are like throwing a tank into a hurricane with the way they drop. However, from experience, they have their place so dont rule them out.
Wow, that was a mouthful....you'd think Id lived this stuff for 10 years for a living....