There are a lot of opinions on breaking in a barrel and different opinions on whether or not it is even needed. I personally believe it is an important process for getting the most accuracy out of your gun. My breakin process is based on an interview with Kenny Jarret that I read many years ago. I believe the article was in Field and Stream but I haven’t been able to find it since. If anyone out there has the article please chime in. This is my current break in process, which originated with that article. I know it is not the “exact” process recommended by Jarret, but very close.
New Barrel Break in:
1. Clean the barrel with wire brush and solvent – always from the muzzle. Then clean with a wet patch and solvent. Finally clean with a dry patch. All ways finish cleaning with a dry patch and make sure the patch is spotless and dry (if patch is wet then get another clean dry patch and repeat).
2. Fire one shot and clean (repeat 3 times)
3. After 3rd shot wrap a patch around a brush (a well-used brush) and JB bore cleaner to the patch (use just enough to coat the patch). Run the rod thru the barrel three times. Remove the cloth and do normal cleaning (step 1).
4. Fire two shots and clean
5. Fire three shots and clean with JB bore cleaner again (Step 3)
6. Fire three shots and clean
7. Fire three shots and clean
8. Fire three shots and clean with JB (Step 3)
9. Finish with oil soaked patch and then another dry patch.
That was for a new barrel break in. For a used barrel:
Step 3 then fire five shots and repeat Step 3
Clean with JB every 300 rounds or so, or if you see your groups getting worse after a lot of shooting. Use JB very sparingly though.
It’s impossible to know if all that actually makes a difference on a new gun. The theory is that copper doesn’t build up evenly where the lands start (where the bullet first makes contact with the lands when the rifling engages the bullet). This process removes excess copper and allows it to build up evenly. Over time copper will build up regardless and needs to be removed. Again it’s impossible to know if it actually makes a difference on a new gun, but I used the above advice on a very old gun: 1944 No4 Mk 1* Lee Enfield Long Brach .303 British. That gun shot 3 ½ ” groups at 100yds before using JB and it shot 0.75” groups at 100yds with factory ammo after. That was an extreme case on an old gun that obviously had a ton of copper fouling, but it made me a believer. I’ve used that process to break in all of my new guns since and I’ve had some real tack drivers. I personal believe that process makes a difference, and I know it made a difference on that particular old gun.
Note: There are a lot of things that can affect the accuracy of a rifle and this cleaning process is not a magic cure all. I used the same process a 1943 No1 MK III* Lee Enfield and it had no affect at all that I could see, but the No1 is a very different animal than a No4. The No1 had other things that also needed to be tuned before I could see any improvement. It now shoots very very well with the tuning and this cleaning process. Most guns have to be individually tuned to get them to shoot their best. For me this cleaning process and break in is the first step in tuning all guns.