Sounds like you purchased an old Sako Finnbear. I own 4 Sako rifles, the first one purchased over 25 years ago. All my Sako rifles are accurate & if your 7mm is in good condition it will be a good shooter. A mate of mine has a 30-06 Finnbear that was made in the late 1970's that still groups well with Winchester supreme factory ammunition. The only way to tell what ammunition your rifle prefers is to try numerous brands.
Id put a Leupold 3-9x40 vx2, or for a little more a Zeiss Conquest 3-9x40.