I'd source a high quality custom 308 barrel in the appropriate twist for the lengths of projectiles you plan to use. I state this because often the quality of a mass produced barrel is questionable and when a custom barrel is fit correctly that also helps with precision.
Every firearm I did this to shot better, some way way better, and most of my better shooting airguns as well partly because either a tested barrel was used, or a high quality custom barrel was used, then the gun was tuned.
Otherwise its a lottery so you buy a new gun and might get anything from a great shooting gun to a horrible shooting guns.
I have a funny tale or you could say a not so funny story.
In my youth and in my search for a precise rifle I bought four or so factory stock centerfire varmint rifles, both new and used, in various cartridges, to shoot Prairie Dogs with at long range. I reloaded and worked up loads the best I could but a 1" group at 100Y was hard to get and between all of them I'd say 1.5" was average. I was disgusted because I wasted hundreds of dollars (back then $300 was a weeks wages) by getting half the guns worth in trade value towards the next rifle.
I walked into a gun store in Prescott AZ and I saw a custom 6mmPPC benchrest rifle with many 100Y targets the owner had shot which were one ragged hole and some done at 200Y. It came with brass, dies, load data, and was $600. It was out of my price range so I walked out of the store but called back a few days later to arrange the purchase but the gun was sold already. Man did that mistake cost me over the years!
It was two decades after this until I finally ended up with my first semi custom varmint rifle that was a half inch TACK driver. But I had spent thousands by then chasing my tail with the lottery of regular guns. However I did luck out and at least get a one rifle and a Contender pistol that shot 1" or a hair less though both had aftermarket barrels.
Oh the stories I could tell. It's fun looking back seeing that eventually my goals were met!
