Accumark in 7mm STW

[Freebore]

I have a Weatherby Accumark in 7STW and it love the Barnes 160's but I would really like to get a better BC bullet like the 162 A-Max to shoot. Tried the Accubond and they were just ok. Tried the Sierra 175's just ok.
Any info would be helpful. I just can't seem to get them to group tight like the Barnes which shoots three rounds into 5/8" at 200.