I don't own a 6.5X55, but my powder of choice in the 30-06 is H4350; in fact, I use the same load in both of my 30-06's with great results (minus the brass of course). The load is 57.5gr behind a Hornady 180gr spire point interlock bullet, with a comparator reading of 3.685 (2.685 to the ogeve). I used to use ww760, but it was dirty as hell, and I actually wasn't getting great velocity.
Mike