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Barrel Care: Do You Need to Break in a Barrel? Really?

To properly care for firearm barrels, follow this ballistics expert's advice to avoid excessive buildup of copper deposits and powder fouling.

Barrel Care: Do You Need to Break in a Barrel? Really?

These are machine marks created during a barrel's manufacture.

There are as many opinions about breaking in (or not breaking in) barrels, and how to clean barrels, as there are shooters. There are few absolutes in these areas. Generally, if something works for you, and you are happy with the results, stick with it! However, I’d like to offer some of my practices and experience on the subject of barrel maintenance.

I’ve worked in or run a ballistics laboratory for 25 years. In that time, I broke in and have cleaned thousands of pressure and accuracy barrels, as well as firearms. What follows is a summary of my findings and what I’ve learned works well. Actual data on anything to do with barrel maintenance is like looking for the Fountain of Youth, which is to say that it is mostly based on opinion or claims made to try and sell you something.

Barrel Care: Do you need to break in a barrel? Really?
This is copper fouling in the grooves of a bore’s rifling.

Barrel Break-In

You could write a book on all the opinions about breaking in a barrel. I’ve heard everything from “there is no need to break in a barrel” to elaborate procedures that approach a surgical operation. The premise of barrel break-in is that there are sharp edges, small burrs or rough spots in the barrel left from the manufacturing operations. These have to be removed or smoothed out before a barrel can shoot consistently, and minimize powder and copper fouling. If you don’t break in the barrel properly, it can initially get heavy copper deposits that will be difficult to remove later. Based on my experience, this is largely true. It comes down to how the barrel was manufactured. Barrels are made by several techniques, which provide widely different qualities of finish and rifling smoothness. Mass-produced barrels usually receive no post rifling lapping, or smoothing, and tend to have lots of machine marks. Bores exhibiting chattering from worn or misaligned reamers and broaches can be a bit rough. Most custom barrel makers these days take the time to carefully inspect their products to ensure few, if any, machine marks exist in the barrel, and then lead lap the bore to polish and smooth out the rifling.

All of the pressure and accuracy test barrels I’ve used in the lab were lead lapped. The rifling in the barrel had been smoothed, but the chamber and rifling’s throat cut by the reamer were not polished and deburred. Most barrel break-ins I did on our pressure and accuracy test barrels were monitored from the initial break-in to observe how performance changed. I can say with certainty that the performance of a barrel changes during an initial number of firings, and the amount of fouling decreases as the barrel is fired.

The break-in procedure I always used was fire one round and clean, two rounds and clean, three rounds and clean, and so on, until I had fired 20 rounds.

Barrel Care: Do you need to break in a barrel? Really?
What you're seeing here is copper fouling at the bore’s muzzle.

I always put the pressure transducers in the pressure-test barrels during break-in, and then I monitored the change in pressure and velocity as I fired them. With few exceptions, the pressure changed typically between 3,000 pounds per square inch (psi) and 7,000 psi. The velocity ranged from 20 feet per second (fps) to 50 fps from the initial firing to when the barrel stopped changing. These numbers varied, depending on the chambering and caliber of the cartridge. Accuracy barrels progressively shot to a more consistent point of impact as they were broken in. The copper fouling in the barrel progressively decreased as the barrel was broken in. With high-quality lapped barrels, usually the change in performance was done in the first 10 to 15 rounds. With mass-produced barrels generally exhibiting a lower-quality surface finish, the break-in could take between 100 and 200 rounds.

The bottom line is that a barrel and its performance change during the initial firings. The number of rounds it takes to get a rifle barrel to settle in varies depending on the quality of the finish of the rifling. A high-quality, smooth barrel will probably take some 10 to 20 rounds to settle in. A low-cost, mass­produced barrel could take upwards of several hundred rounds to break in. If you don’t clean the bore frequently during this initial period, especially the first five to 10 rounds, you’ll leave a lot of copper in the barrel that will require work to get out later.

Barrel Care: Do you need to break in a barrel? Really?
This is what wear-in lead of a bore’s rifling looks like.

Barrel Cleaning

The whole point of cleaning your barrel is to prevent the excessive build up of copper deposits and powder fouling in the barrel. If this fouling is allowed to accumulate and is not cleaned out, it will eventually affect the pressure, velocity and accuracy of the barrel. Cleaning at regular intervals will prevent heavy buildup of fouling and make it much easier to remove the fouling that is in the barrel.

There are several rules of thumb that apply to barrel fouling. As I already described, the surface finish and smoothness of rifling plays the biggest role in how a barrel will foul. Rub a bullet with a piece of glass, or conversely a file, and you’ll see a big difference in the amount of copper left behind. Bullet velocity plays a big role in fouling, too. The higher the velocity, more copper is going to be scrubbed off. The hardness of the bullet is a factor, also. The less give the bullet has, the more copper it will leave behind. A thin-jacketed lead-core bullet will leave less copper behind than a solid-copper bullet or a hard-core armor-piercing bullet with a copper jacket.

Barrel Care: Do you need to break in a barrel? Really?
Sharp Shoot R wipe-out bore cleaner, 5 oz.: $15

I have always found carbon fouling to be the most difficult thing to remove in a barrel. It usually appears the worst in the throat and then steadily decreases as you inspect towards the muzzle. I have never found a chemical cleaner than will really get the carbon fouling out of the grooves. (If a reader is aware of a product, please write and let us know what you use.)

When a barrel obviously has black deposits in the grooves, the only thing I’ve found that can get it out is a paste such as J-B Bore Cleaning Compound (, or a very fine polishing compound such as 800- to 1200-grit lapping compound on a tight-fitting patch; then scrub the barrel. Be careful with the lapping compound though and don’t overdo it; you could start to scrub the throat out of the barrel, especially with a smaller bore such as .17 or .22 caliber.

Regular cleaning will help you to keep up with the carbon fouling and not let it get to the point where you have to scrub the barrel with lapping compound. The smaller the bore, and the slower the powder speed, the more rapidly the carbon fouling will build up. Large-case .22 through 6.5mm calibers seem to be the worst for carbon fouling.


Barrel Care: Do you need to break in a barrel? Really?
Here is heat-checking in the throat of a barrel.

There are many cleaners out there that will get the job done for removing most of the powder fouling and copper. I have tried most of them. The cleaners I‘ve settled on are the foaming spray cleaners. They completely fill the bore and cling to the bore for a long period of time. This is not an endorsement, but I use SharpShoot­R Wipeout spray cleaner ( There are few products I have used that remove copper faster than Wipe-out (other than ammonia-based products). Another advantage of Wipe-out is that it does not require brushing the bore. If you have heavy copper buildup, an ammonia-based product such as Sweet’s 7.62 bore cleaner ( is one of the best. I have often used Sweet’s 7.62 to get copper out of old military rifles that were never cleaned with a copper solvent. It removes copper quickly, but be careful with any ammonia-based product. Don’t let them sit in the barrel for more than about an hour. Depending on the steel of your barrel, ammonia-based products can etch the surface of the bore if left long term. I would also encourage you to purchase a plastic-coated, one-piece cleaning rod that is the right size for the bore of your gun, along with a correctly sized jag for patches. The one-piece plastic-coated rod will prevent damage to the lead of the rifle or crown of the barrel. Do not use a multi-piece cleaning rod. The joints will eventually damage the rifling.

With smallbore rifles, particularly of .17 caliber, don’t use a wire brush much either. These brushes have stiff bristles that will wear out the throat’s rifling quickly because .17-caliber bores have small lands. Allow me to offer an experience to back this up: When bullet and ammunition production was first started on the .17 HMR, we at Hornady religiously brushed the accuracy barrels after every test. On the first batch of accuracy barrels, we only got about 1,500 rounds out of them before we started to see the accuracy fall off. When we borescoped them, we discovered that we had brushed the rifling out of the first inch or so of the barrel. After that, we just used a copper solvent and no brushing. The accuracy life of the barrels went up to about 7,500 rounds.

Lastly, if you brush your bore, never use stainless-steel brushes. They will scratch your barrel’s bore.

Barrel Care: Do you need to break in a barrel? Really?
TESLONG NTG100 Flexible Borescope: $46


All the in-bore images in this article were taken with a borescope. You will find nothing else that lets you see what’s really going on in your barrel like a borescope. Rifling wear, heat checking in the throat, carbon or copper fouling and machining marks can all be seen in stark detail. I’m going to push borescopes here because the borelights that are used frequently in gun shops to show you the bore’s condition can make a really lousy barrel look good. A bore that looks good with a bore light can look much worse with a borescope.

You don’t have to spend the price of a nice rifle to get a borescope that will yield good images. The recent proliferation of USB borescopes in the $65 to $130 range provide very good images. All the borescope images in this article were taken with a NTG Rifle Borescope ( Lyman offers its Borecam Pro Wireless that sends images to your cell phone ($355, I have used a Lyman Borecam for about five years, and it has proven to be a great value. The pinnacle of borescopes is the Hawkeye Rigid, which starts at $1,445 ( Prices vary depending on the length of the borescope and the optional accessories desired. If you are into collecting old firearms, like I am, a borescope will save you from making expensive mistakes.

One last observation: Many of you have heard about the “clean, cold-bore shot,” and it usually doesn’t go where we want. In my experience that is absolutely true; I verified this phenomenon for myself. Therefore, I usually fire two or three fouling shots in a clean bore to help it settle in before I ever do any serious shooting.

I recommend that you consider a bore cleaning every 100 rounds. Doing so will prevent heavy fouling build-up, which can be hard to get out. This will help to maintain your rifle’s consistent performance and accuracy.

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