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When you buy a new rifle, there’s a chance that the inside of the barrel — the bore — may need polishing due to manufacturing flaws. One way you can polish the barrel is by shooting out the roughness.
Barrels and Break In
The barrel is one of the core components of a firearm. By containing and directing a controlled explosion, the barrel facilitates the propulsion of a projectile toward a target. The 15th-century invention of rifling increased the effective range of ammunition by imparting a gyroscopically stabilizing rotation to the bullet.
When a firearm leaves the factory, regardless of whether it’s a bolt-action sporting rifle or a semi-automatic pistol, it may need loosening up. The tolerances between working parts may be too tight, causing sluggish operation. Springs may be too stout. The manufacturing process may have left machine marks or burrs. Firing a couple of hundred rounds of ammunition tends to solve this problem in pistols and semi-automatic pistols.
However, barrels are another matter. When you fire a copper-jacketed or gilding-metal bullet through a rough barrel, the roughness of the bore can cause the bullet to leave copper deposits, reducing the inherent accuracy of your rifle. As a result, it’s necessary to introduce a degree of smoothness to the inside of the barrel, eliminating tool marks and inconsistencies in the bore.
How to Break in a Rifle Barrel
Before learning how to break in a rifle barrel, you should always clean a new rifle before firing it. A new rifle barrel may have oil or grease inside the bore. Alternatively, it may have accumulated dust or other contaminants if it’s been lying on a rack or sitting in a cabinet.
Barrel manufacturers use different production techniques and quality-control systems. High-quality custom barrels manufactured for precision shooting are very different from mil-spec contract barrels.
The roughness that a barrel maker leaves can potentially interfere with the rifle’s accuracy, as the interior surface of the bore causes each bullet to deposit copper fouling. One way to resolve this is by breaking in the barrel. This refers to a specific process of deliberately inducing wear by firing multiple rounds of ammunition and then cleaning the barrel.
The underlying principle is as follows: bullets, particularly those with a copper, cupro-nickel, copper-zinc, or gilding-metal jacket, can impart a lapping effect, polishing the bore.
However, for this process to be effective, you can’t simply fire 200 rounds of ammunition in one session. You need to fire one or two rounds at a time, then clean the barrel before continuing. Usually, you’ll only need to perform this process for a maximum of 10 to 20 rounds. However, several factors directly affect the number of rounds you’ll need to break in a barrel. These range from the barrel’s composition to how it was manufactured.
For example, in a cold hammer-forged barrel, the manufacturer does not cut the rifling grooves into the bore. Instead, the barrel maker places the barrel blank on a mandrel and hammers the outside, reducing its length and diameter and causing the mandrel to impart the rifling pattern on the inside of the bore.
Breaking in a rifle barrel can be the user equivalent of hand lapping the bore. First, fire a single round of ammunition. You need to determine the extent of the copper fouling — i.e., the extent to which the bullets deposit copper residue or particles in the bore — and how difficult this fouling is to remove.
Clean the Bore
You should use a phosphor-bronze bore brush to scrub the fouling free in between shots. Always ensure that you’re using a bore brush compatible with the caliber of your firearm — you need a snug fit for maximum effect.
Dip this brush in a high-quality cleaning solvent that can effectively dissolve fouling and attach the brush to your cleaning rod. Insert the cleaning rod into the bore from the breech end and scrub the inside of the barrel thoroughly, depositing the solvent. Let the solvent work for a few minutes.
Next, remove the bore brush and attach a slotted tip or jag to your cleaning rod. Force a cleaning patch, soaked in solvent, through the barrel from the breech end to the muzzle in one direction only.
When the patch exits the muzzle, remove the patch. Don’t remove the patch from the breech end — you don’t want the soiled patch to redeposit any fouling you removed. Let the solvent work again for a few minutes. Repeat this process with clean patches.
It’s important to only use white, clean patches. You’re not only using cleaning patches to deposit solvent and wipe away the dissolved fouling — you’re also using them to identify the type and extent of the fouling. If the cotton or flannelette is colorized, it may not adequately disclose this information to you.
If you’re concerned about pushing the cleaning rod all the way through the barrel because it may fall and contact the crown, potentially damaging it, consider buying a bore guide. A bore guide will ensure that the cleaning rod remains in the center of the bore at all times.
Although you may be tempted to thrust the cleaning rod through the barrel fast, there’s no need. Apply pressure gradually and run the rod through slowly.
Always Clean the Chamber
In between shots, when you’re cleaning the bore, don’t neglect the chamber. Use a proper chamber cleaning brush, solvent, and patches. Pay particular attention to the chamber and the throat — these parts of the barrel must remain clean for you to determine the effects of your breaking-in procedure.
Inspect the Barrel
You should examine the bore before and after firing and cleaning to determine the extent of the fouling. A borescope can help you in how to break in a rifle barrel. It will show you the presence of tool marks and where copper fouling collects, allowing you to know when you need to cease firing and resume the cleaning process.
However, borescopes aren’t available to every shooter. That doesn’t mean your inspection procedure should suffer. Unloading the action, opening the breech, and shining a bore light into the chamber can also reveal marks and fouling deposits, albeit with less accuracy.
Do I Need to Break in a Barrel?
The answer to this question is complex. Neither firearms manufacturers nor enthusiasts agree on the precise break-in procedure or even whether it’s essential. You may decide that you want to gain every advantage possible. After all, firing a few rounds, cleaning the bore and chamber, and repeating this exercise can’t hurt.
However, if you decide that you only think an initial cleaning is necessary, proceed that way. The type of barrel you have also determines the necessity of this process, assuming you agree that it delivers results.
Whether you decide to break in your barrel or not is up to you. If you think the procedure is unnecessary, you’re under no obligation to partake of it. However, if you believe that breaking in your rifle can benefit you, there are specific guidelines you can follow.