Solitar
The problem with longer barrels is that you get diminishing returns with the longer length. Eventually the minuses, such as drag, friction, concentricicy<sp> of barrel etc outweigh the advantages of the longer barrel. Each caliber and twist rate is different, even different barrels from the same lot will probably shoot different. A lot depends on what you call accurate. If you're looking for a hunting rifle then most likely 1 moa or so is sufficient, whereas if you're into 1000 yd silhouette or benchrest, that won't even get you into the ballpark. Again, depending on caliber and twist rate, a 16" or 18" barrel may work as opposed to a 36" barrel. Though for serious benchrest accuracy, a longer barrel seems to help, along with the wildcat cartridges, recoilless benchblock actions, electronic solenoid triggers etc.
From what I've read, long range high-power silhouette is a completely different world. I've been into firearms for 30 years and I didn't recognize a bit of the nomenclature. Even some of the calibers I'd never even heard of, such as the 6 Fatboy etc.