Decopper your barrel with Sweets 7.62. Unless you have 10,000+ rds through your 308.
Check the Scope ( Buy, a Leupold or, Burris,.. IF, Necessary ! ) check Crown & Brake alignment/ bullet clearence, Re- Torque and ABSOLUTELY CLEAN, ALL, the Copper and Carbon out ( CLR and C-4 Carbon Remover ! ) , Get the" Krap" OUT of, the barrel and "Throat" as stated, above !
Yup, that means, 2 or 3, Cleanings and soak the Brake, in CLR !
THEN, If all else fails and Rifle still does NOT shoot, up to "expectations", Buy a Tikka, as they are about, the Price of,..
a New Barrel, Installed by, a competent, Gunsmith !