I had several .2506's and the 120gn never shot well out of any of them!
My current quaterbore is a 1:12 twist so I'm good for 100gn and below. I use factory Feds in 100gn B/Tips there are fine assuming you place the x hairs in the right bit. I may try a few 115 grainers to see if they will stabilize.
85 gn - is a stonking fox round, very fast and pole axes them. Only trouble is possible throat erosion.
In a Ruger MK2 I used a 115 Nosler B/T with I think 51.5 grains of Reloder 22 and it grouped well at 100yds.
It is a great round but a but fickle to get right on bullets and powder, Sako cases are pretty good quality for reloading
Hope this helps