I believe you have an 8x57 Mauser target rifle - The CG-63 - introduced on May 1, 1963 by the Carl Gustafs Stads Gevarsfaktori. (CG)
During the production period CG made up around 60,000 target rifles.
Almost all used existing M-96 rifle or M-94 carbine actions which were inspected to make sure they were super straight. Although some Husqvarna actions have also been used.
AFAIK, The standard CG-63 barrel was a free-floated heavy barrel which measures 19.0mm at the action, tapering to 17.5 mm at the muzzle.
The rifling twist rate for most CG-63s is 1:220mm. (the M96, M38, & M94 all had a 1:200mm twist rate)
The CG-63s were also made in military versions called the M6 and M7 - but w/o a pic or a more complete description - IDK which you have.
The standard target ammunition for the CG-63s was originally a 140gr Boatail bullet with a muzzle velocity of about 2,600 fps.
Some CG-63s have glass bedded actions and some have steel stock inserts.
The first CG-63 sights were Carl Gustafs GF micrometer receiver sights with a 2mm aperture.