I know every rifle is different and all that but my wmr was very ammo fussy. It was however just bad bedding. When I fixed it it was suddenly hard to decide which ammo was worse, they all grouped all of a sudden!
Sounds like this may also be a trait of hmr too! It's ok, I'm use to fixing this kind of thing.
I've got to refinish the stock so will be checking the bedding also ?