I read this on Varmit als web page. I tend to think the same way for break in. Why spend so much in ammo to do the same thing with the jb a lot faster.
NEW BARREL BREAK IN.... There is so much black magic out there about breaking in a barrel, that I am not going to suggest any procedure. I will merely tell you what I do with a new barrel. I take the brand new barrel and use J-B on it. That's right, I clean and polish it with J-B before even firing the first round through it. I put a light coat of J-B on a patch and give the barrel about 50 strokes from end to end with it. Then I clean the J-B out with a couple of patches of Shooter's Choice MC#7. I dry the bore with 3 or 4 patches until it is completely dry. I carefully clean the chamber of J-B too. That's it, the barrel is broken in and I am ready to sight in, shoot some groups, and work up an accurate load. I take the rifle to the range and shoot 3 or 4 five shot groups with Moly-coated bullets. I clean the barrel with Sweet's 7.62 and usually there is no copper. From then on, shooting only Moly-coated bullets, I clean the barrel when I feel guilty. If there is copper on the first cleaning, I conclude that I didn't do enough with the J-B and repeat the J-B treatment. All that these shoot-clean, shoot-clean, etc. break in processes do, in my opinion, is perform a slow, inefficient, and expensive polishing process which the J-B does better, smoother, and faster. I use a plastic coated stainless steel cleaning rod and a jag style that you wrap the patches around. I use the blue Shop Towels for patch material and I cut a roll into a number of 1-½-inch wide rolls with a sharp knife. I never use brushes in my barrels and I don't even have any. I use J-B, Shooter's Choice MC#7, and Sweet's 7.62. I am sure there are other procedures that are just as good or superior, but this works very well for me. If I have a particularly bad copper fouling barrel, I use Flitz Metal Polish instead of JB. Here and you can see what Shilen recommends for breaking in a new barrel.
NOTE. A J-B patch will turn black even after the barrel is clean so you shouldn’t try to clean a barrel with J-B until the patch remains "clean".
WHAT IS J-B?... J-B Non Embedding Bore Cleaning Compound. My two ounce jar of J-B has lasted me for 15+ years and is still going strong. It is a bore cleaning compound that polishes the bore. Here is more info I have just received and verified on J-B. Page 229 of Brownells' catalog #50 has a complete write up on the "J-B bore cleaning compound". It claims this to be the original formula developed by Jim Brobst (Jim Brobst is the name on my old jar of J-B) and produced under an exclusive license. From them, a two ounce jar sells for $5.95. Brownells' phone number is (515) 623-5401.
