| Also called burnishing, this admittedly tedious procedure is neccesary if one is to get the best accuracy possible from one's new rifle.
The idea is to burnish or smoothen out the bore of the rifle by having the residual copper material fill in all the microscopic imperfections on the surface of the bore. Even mirror smooth bores have tiny imperfections that is invisible to the naked eye. It is better to have these imperfections smoothed out by getting filled with the copper jacketing of your bullet rather than it get filled with assorted gunk like bore cleaner, carbon deposits and copper or lead residue. This procedure is only needed for new barrels and need no repetitions after it is done.
You will need a bore brush, a lot of dry cotton patches, a bottle of copper solvent and about 100 rounds of FMJ ammo in the caliber of your rifle, preferably premium factory loaded stuff. Hornady, Winchester, Federal, or Remington ammo will be perfect. Start by cleaning the bore by passing a patch saturated in your copper solvent, then a few passes of the bore brush then another wet patch, followed by a dry patch. I told you it was tedious. We only have begun.
Fire one shot and clean the barrel thoroughly. This means brushing and passsing wet and dry patches alternately until no discoloration is seen upon passing a wet patch. You will repeat this ten times.
Next thing you will do is similar to the abovementioned procedure but will now be 5 shot intervals between cleaning.
Finally you will do the 5 shot then clean procedure again while also taking note of the group size you are making.
If you are not yet very proficient with the rifle, you can use a sandbag or benchrest to aid in shooting accurately.
After the shooting session, thoroughly clean your rifle again and lube for storage.
For people who are expert marksmen using a match grade rifle and match grade ammo, noticeable improvements on accuracy might be observed until the rifle has hit the 400 round mark. At which point, you have done all that you can and it is your raw skill that will need improvement to achieve better and better accuracy.
Note that most people probably can't shoot as good as their rifles can. It will takes lots of ammo and lots of practice to "outshoot" any decent modern rifle. | 
