If you're a benchrest shooter, you might want to look at the guy winning the matches and find out what he's doing right.
Otherwise, clean the bore after every shooting session and the same goal is being accomplished as the typically recommended break-in but without all the hassle. It might take a little longer before the barrel smooths out, but that's not going to change the shooting performance of the gun in most cases.
If the gun won't get through a shooting session without starting to show accuracy degradation due to copper fouling buildup, then you might want to consider getting the bore lapped, or maybe cleaning more frequently to remove the copper fouling and to speed the normal burnishing process.
If the bore is already lapped, and the lapping was done right then you shouldn't need any sort of break-in at all.