Being a 6.5, most game weight bullets, the 120, 130, 140 class have very good sectional density for their weight. Generally they have the same SD as a .270 bullet that weighs 10gr more. You should be right around 2800FPS in your 'x47 so you have quite a bit of range capability.
Given that spec, I wouldn't hesitate to take a poke at the largest mulie at <400 with a 120 or 130gr high BC bullet. I would stay away from solids if I were you though.
Are you comfy at that range with that rifle? If not, practice up!
My 6.5 is based on the .257 Roberts case that has been Ackleyd, so I have a little more speed at the muzzle, and am willing to reach a little farther with my 120s. I may try the 130s this year though.