I shoot both the 250g and the 290g T-EZ in my ML. I use 120g BH209 and ditch the supplied sabots for MMP HPH-12 sabots. They group a lot better in my rifle. I too have noticed that the flat based Barnes' shoot better for me. I shot quite a few of the boat-tails and I wasn't impressed.

All I use with these bullets is 120g BH209. I have been told that you want a stouter load because of how long the Barnes bullets are. Something about helping them stabilize in flight. All I know is this combination shoots great for me.