Re: Barrel Break-in
My take on barrel break in is this. All you are trying to do is smooth out the very last rough spots and burrs in the rifling. You can either use a bullet - as was described in the other posts, or you can manually polish it.
For any quality BR type hand lapped barrel, I just shoot and clean a bit. They are usually so smooth that fouling stops after a bit of use.
For production or aftermarket unlapped barrels, I polish with 320grit, JB bore lapping compound and reg. JB.
The procedure is simply to put some of the 'grit' on an oil soaked cotton patch and run back and forth in an oily bore. You will feel the barrel smooth up. I only run the 320 grit back and forth 20 times or so then clean and check. Repeat if I feel or see rough spots ON TOP of the lands. Machine marks below the surface just don't matter.
Easy test is to run a dry cotton patch down the bore. Lint will be collected on the burrs.
I then switch to the red JB. This is like jewellers rouge. A very light abrasive. Go at it for maybe 50 stokes. Things will really start to feel smooth.
I then switch to reg. JB and go for 50 or so more. The bore will be brilliantly shiny.
All this takes about 15 min to do and doesn't put any wear on the throat or wallet. I do not polish much in the throat area.
Barrel is now broken in.
A bore that copper fouls can still be very accurate. Many of my barrels that shoot tiny groups also show visible green/copper in the bore. Don't get hung up on fouling. Worry about how well it shoots. I do periodically polish with the JB stuff. Eventually, the bore will reduce in fouling but usually never stop.