1. If the rifle does not have a new barrel, explain the process for lapping and breaking in the bore.
Before I start the process of lapping or breaking in a barrel, especially one that is not new, I will take a bore scope to the barrel and inspect the lands and grooves for damage, rusting or pitting. It is possible that the barrel is beyond repair and that a new barrel is the only real solution to fixing the issue. If I have determined that lapping may fix the issue and not just a quick cleaning, then I may decide to lap the bore or even fire lap the barrel. This may clean up some of the barrel’s issues and make for better spin on the round and give the individual user a better shot group at distance.
Nathan Foster, the author of The practical guide to bolt action accurizing and maintenance, mentions bringing a wide range of things to the range when breaking in a rifles barrel. These items include things like cleaning rods, bronze brushes, copper solvent, degreaser, 4x2 patches, and Autosol. He goes on to say that many copper solvents are “Truly, utterly useless, pointless liquids.” And that “You would be better off taking leak down the bore.” (Foster, 2014, page 85) A good way to see if your copper cleaner works well is to try some on a copper FMJ and to look for a reaction. The solution should breakdown the copper and it should have an etched look if it works well. Cleaning the rifles barrel is important and copper fouling can cause accuracy issues. A good copper solvent may solve the problem. So, let’s cover hand lapping the bore and why it is important. For new rifles this may remove factory burrs and improve the finish but with older rifles this can be considered part of your barrel’s regular maintenance. By taking a bronze brush and a maroon colored poly pad you can lap the throat section of the barrel by running these back and forth inside the first 3 inches of the barrel. This helps remove some of the factory machining marks. Next you will repeat the process in the rest of the barrel stopping at about 3 inches from the muzzle. Nathan Foster says you should “get in there and give that barrel a good kick in the pants.” (Foster, 2014, page 89) This means you should really work this section and not worry about damaging the rifle. Finally, you want to work the muzzle end but, in a careful, controlled manner. Allow the brush to exit the muzzle a little bit but do not totally remove it with each stroke. Only 8-10 strokes are recommended. Then you can use the Autosol he mentions on the worn pad to run through the barrel again to try and get a clean finish to the inside of the barrel.
2. Briefly summarize “fire lapping” and explain the purpose of this procedure.
Some people would prefer to work the barrel using a method called fire lapping, but Nathan Foster says this should be considered a last resort. Fire lapping is the process of adding a cutting grit to the projectile and firing it through the barrel in an effort to fix any issues the barrels lands may have. A burr halfway down a barrel is going to affect the projectile and make for a less accurate shot. Doing this may also correct any abnormal bore dimensions and give you a consistent grip and twist on the projectile. This takes time if you do it correctly so be sure not to rush this process. One approach is to start with a 220-grit on five rounds and clean the barrel after every shot. This prevents buildup and allows each bullet to do its job. Then, even though Nathan Foster doesn’t recommend it, move to a 320-grit compound, and fire another 5 rounds again cleaning the barrel after every shot. Finally use a much finer 600-grit compound on the projectiles and fire your last 5 rounds again cleaning the barrel aftereach shot. If you decide not to clean the other grits out as you fire, then you may expect mixed results asthe grits build up and mix.
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