Breaking in a barrel… What does ‘breaking in a barrel’ mean, and should you care about it? Well that depends on just how interested you are with the barrel’s accuracy and longevity. Make no mistake, breaking-in a barrel is a tedious, and yet necessary, process if you want to get the very most from a good barrel.
Unfortunately, the simple and straight forward procedure sure seems to be badly misunderstood, at least based on what the self-proclaimed expert knuckleheads say online. A good deal of the information posted about breaking-in a barrel seems to be unclear or misinterpreted about the why and how of the process. With that in mind, I will attempt to provide some clarity to the reasons why, and the process itself.
Understanding Break-In
Let me begin by saying that many believe the barrel to be the heart of the rifle. If that is so, and I believe it is, we should know all we can about it. As the heart of the rifle, the barrel is the foremost contributor to a rifle’s accuracy. If that is also true, the rifling must be the rifle’s soul.
I suppose, for this little treatise, I should tackle the most controversial and misunderstood concept first. “No matter who made the barrel, or how carefully it was finished, there are going to be manufacturing imperfections that only affect the accuracy of a bullet being fired through it.” So, let’s start with that.
Your new rifle or barrel was no doubt shipped to you with a short-term rust inhibitor in the bore to protect it from corrosion during storage, shipping, etc. Upon receipt of your barrel, you should first review the order and packing list to make sure the barrel matches what you ordered. If it does, clean the bore and apply a product suitable to the length of time it will be stored.
Preventing oxidation and corrosion in the barrel is your responsibility as the customer. Barrel makers are not responsible for a barrel that has been improperly stored, neglected, or abused by the distributor or customer.
It’s important to understand that even the most expensive, hand-lapped custom barrel will have a few tool marks in the barrel and throat from the chambering process and will benefit from a properly executed break-in procedure. A premium barrel, that has been finish lapped, will have the direction of the finish following in the direction of the bullet travel, so fouling will be minimal compared to a less expensive barrel with internal tooling marks.
This is true of any properly-lapped barrel regardless of how it’s rifled. If it is not finish-lapped, there will be reamer marks left in the bore. The reamer marks will be directly across the direction of the bullet travel. This occurs, even in button-rifled barrels, because the button cannot completely iron out the reamer marks.
Because the lay of the finish with a premium barrel is in the direction of the bullet travel, very little change occurs to the bore during break-in. However, the throat is another story. When your barrel is chambered, there are reamer marks left in the throat that cut across the lands and the direction of the bullet’s travel.
In a new barrel, the reamer marks are very distinct; some say they appear much like the teeth on a fine file. When the bullet is fired and forced into the throat, copper dust is removed from the jacket material and released into the gas, which at this temperature and pressure, forms a plasma. The copper dust is vaporized in this plasma and transported down the barrel. As the gas cools, the copper drops out of suspension and is deposited in the bore.
This makes it appear as if the source of the fouling is the bore when it’s actually from the throat. Copper adheres well to itself. If that copper is allowed to stay in the bore (with additional bullets and deposits fired over it), the buildup will affect performance and be more difficult to remove later. So, when we break in a barrel, our goal is to get the throat “polished” without allowing copper to build up in the bore. This is the reasoning for the “fire one shot and clean” procedure.
Every barrel varies a bit in how many rounds it takes to break in. A chrome moly barrel may take longer to break in than stainless-steel barrel, because it is more abrasion resistant — even though it is of similar hardness. Also, chrome moly has more of an affinity for copper than stainless steel, so it will usually show a little more ‘color,’ if you are using a chemical cleaner. Remember to keep the barrel clean while breaking in the throat by firing bullets through it.
That said, more affordable, lower-cost barrels are going to have more pronounced imperfections within the bore. Those imperfections are most commonly tool marks resulting from the drilling and rifling processes. Additionally, if it’s a semi-automatic, such as an AR type, there is a good chance that there could be burrs where the gas port was drilled. Those barrels will benefit even more from the break-in process.
The goal of breaking in a barrel is to have it shoot to its full potential sooner. It also means there won’t be as much copper fouling during extended use. Understand, a barrel break-in procedure does not provide a longer barrel life. However, it does provide top accuracy earlier in the barrel’s life. That results in a longer (top accuracy) life and better performance.
So, if those are things you are interested in for your barrels… The barrel break-in procedure is for you. Go ahead and knock down those manufacturing imperfections by smoothing or polishing the interior surface and burnishing the barrel steel via the bullets fired through it. Remember, the bullet is not removing metal from the barrel like an abrasive, it’s just displacing it. The bullet functions much the same as running a knife on a steel as opposed to a whetstone.
One could correctly say that all barrels eventually break-in. However, unless this is a deliberate process done at the outset, the barrel could be worn out before it’s broken in. It’s the process of firing one bullet down a clean barrel that provides the burnishing effect.
So, why not just fire one bullet through a clean barrel each time you go to the range. Then, after enough visits to the range, the process will have had its effect. The problem with that is it might not happen until after lots of trips to the range. The process I am explaining will, or should, provide the desired burnishing results in one or two intensive range session — if all goes well.
The following is a guide to “barrel break-in” based on my experience and is not intended to be detailed instructions. Some barrel, chamber, bullet, primer, powder, pressure, or velocity combinations may require more cycles than others. That means, it’s a good idea to pay attention to what the barrel is telling you with its fouling pattern and what you see on the patches. Once the barrel shows signs of having been broken in, there is no need to continue the process.
To start, you should perform the ‘shoot one shot and clean’ cycle for a minimum of five shots. Shoot- clean, shoot-clean, and repeat firing only one round at a time. If the fouling is not reduced, fire five more rounds and so on until fouling begins to drop off. At that point, shoot two shots before cleaning and observe. If fouling is reduced, fire 3 shots before cleaning. When fouling is further reduced, fire 5 shots and clean until it does not foul.
Success, and a merciful end to the tedium, is based on how much the copper fouling is reduced with each cycle. Hopefully, if it’s a “good” barrel, that will be sooner than later, and there won’t be anything showing on the patch. At that point, shoot 5 to 6 rounds and patch-clean the barrel. That’s the test, to see whether the patch comes out clean (no bluish-green residue). If so, you are done and out of your misery. The barrel is then broken in, if it indeed will break-in. Here is the procedure adjusted for different types of barrel materials.
Stainless-Steel Barrels
- Five to 10 one-shot cycles
- Three to 5 two-shot cycles
- One to 5 three-shot cycles
- One to 3 five-shot cycles
Chrome Moly Steel Barrels
- Five to 25 one-shot cycles
- Five to 10 two-shot cycles
- Two to 5 three-shot cycles
- One to 3 five-shot cycles
Additional Procedure Notes
- Clean the powder residue from bore using a solvent such as Shooter’s Choice or Butch’s Bore Shine following the instructions on bottle.
- Follow with a second group of patches coated in Birchwood Casey Bore Scrubber, Gunslick Pro Gun-Flush, or (for the more financially conscience) brake or carburetor cleaner from the local auto emporium or similar solvent followed with dry patches until all residue is removed from the bore.
- With a copper remover, such as my choice Sweets 7.62 Solvent or Montana X-Treme Copper Killer to remove copper fouling. Follow the instructions on bottle.
- With a second group of patches coated in Birchwood Casey Bore Scrubber, Gunslick Pro Gun-Flush, brake or carburetor cleaner, or similar solvent followed with dry patches until all residue is removed from the bore.
- Run a patch that is lightly coated with a gun oil such as Lucas Gun Oil, Break Free, or a similar light oil.
- Finish with a dry patch to remove excess oil from the bore. Firing the rifle with excess oil left in the bore can cause higher chamber pressures and is not recommended.
Dos and Don’ts
- Use a one-piece, coated cleaning rod such as Dewey manufactures.
- Use a bore guide.
- Clean from the chamber end only. Never use a stainless-steel bore brush. Do not leave strong ammonia cleaning products in your bore for extended periods of time.
- Do not allow solvents to contact the stock. They can remove the finish.
Once the barrel is broken in, remember to clean the barrel after every 20 or so rounds to keep accuracy optimal. A dirty bore is a primary cause of poor accuracy. You should understand that some barrels are going to be rough enough that a bullet jacket won’t get it done. You could shoot and clean until the cows come home, and some barrels are still going to show fouling. When that happens, I have been known to use JB Bore Paste, but that is another story.
Finally, in the spirit of full disclosure, there is also a product that was developed by David Tubb, Camp Perry Long Range champion, and national record holder. The Tubb Final Finish Bore Polishing System, which I have no personal experience with, is composed of a series of 50 bullets that are impregnated with 5 different progressively finer compounds that are designed to polish out bore imperfections. Good luck and Good Shootin’. Stay safe, train often, and practice, practice, practice!
Buy it, clean it, shoot it a little (10-20 rounds), clean it again and call it good. If there are national and world champions that don’t hassle with it, It’s probably not that big of a deal.
Eric Cortina has a 1.1 inch 5 shot group fired from 1000 yards to show for his procedure of no barrel break in. He keeps his rifle consistently clean but does zero break in for a new barrel. As a World Record holder I listen to his advise.
Thanks for this most informative article; it’s exactly the formula I’ve followed on rifles for many years and many guns (now) both new and used. The only slight difference being the use of (some) different solvents and copper removers.
I have found this process works well in many cases on used rifles, as well.
The key is learning to “read” the patches. It’s easy to tell when your powder solvent has completed its work, but it takes a tad more patience with the copper solvents. In fact patience is the key to the entire process, but if you stick with it, I firmly believe it to pay off in the end with better accuracy, an easier rifle to clean and a fuller understanding of the individual rifle itself.
Lastly, some 25 years ago I began to use surgical gloves during the cleaning process and nylon (Tyvex) brushes vs. the copper brushes, which seem to lay out a fine layer of copper/brass (?) during the cooper solvent stage of cleaning.
Always, always, always! (For accurate rifles) For ARs, AKs, plinkers… There no point.
While not an elite shooter I am a US Distinguished Rifleman and a two time President’s Hundred recipient, NRA High Master Rifle, and I’ve won a couple of State Championships. I get a new barrel on my AR competition guns once a year. I always start a new season with a new barrel. I use less expensive Wilson barrels so I just pitch them at 3k rounds. I also shoot benchmark, criterion, and others. On a new barrel I clean, shoot 5, clean, shoot 5, clean, shoot 10, clean, done. I only use hoppes no. 9, only cotton patches, from the chamber when possible, only in the direction of bullet travel (remove patch as it comes out of the barrel) when possible, always finish cleaning with 4 dry patches, always use a guide, always use coated cleaning rod (Dewey). I use Hoppes for cleaning and CLP or Go-juice for lubricant. I clean after events where I have shot 264 round (88 for each of 3 days CMP Cup), between cleaning. The only accuracy problem I’ve experienced is me. I’m concerned about damaging barrels from over cleaning, I’m very gentle and careful when I clean. I don’t believe in rigorous break-in, cleaning, uniforming bullets, using lab scales to weigh powder, etc. Use a good barrel, good components, and shoot. If you want to be a good shot….shoot a lot, but shoot with a plan, take notes, develop a shot process. That will do more for accuracy than any cleaning regime. IMHO.
Do NOT use a chamber guide. If you do, you should clean the “leade,” or portion between the case mouth and chamber throat after removing it. Failing to do this can cause severe buildup of a carbon ring in some rifles, making chambering difficult or impossible, even pulling the bullets on extraction if you do manage to chamber one. So, if you have to clean behind the chamber guide, why are you using it?
My friend is assistant manager at a Sporting goods store. He got a 6.5 prc with a titanium barrel. I asked him when we went to the range to sight it in don’t you have to break it in he said the manufacture said no it’s a Christensen!
Any thoughts on that or are you just talking about specific barrels?
“Cleaning the necked in portion of the chamber, like where the bullet leaves the brass, and a rather dirty deposit of metal and carbon.”
p.s. When doing this, it did seem to reduce my group size, so was wondering if it should be included in this “break-in” process?
This is one topic I have heard passionate arguments for both extremes and everything in between. One guy will say barrel break in is “complete bullspit!!” … Next guy: no no no it’s absolutely vital to do EXACTLY ‘this’ or ‘that’ or often something voodoo like.
Appreciate Ed’s take on it. Good article and thanks to CTD for offering it to us.
I can’t say if performing a break-in will enhance accuracy because I don’t recall ever performing such a task. I don’t see how it’s possible to know if a break-in actually helps, but I’m sure it doesn’t hurt. I do swab the bore of a new rifle and clean any bore after most shooting sessions. I have never experienced any notable change or degradation in performance as a result of this. I suppose accuracy could suffer initially with any barrel, but after 25 -100 rounds and some proper cleaning, I suspect any burrs will have been removed.
Excellent article, especially for anyone who has obtained their dream rifle, or has plans for passing one down for generations to come.
One area I wonder how much impact it might have on this issues is: Cleaning the necked in portion of the chamber, like where the bullet leaves the brass, and a rather dirty deposit of metal and carbon. I know a chamber brush for ARs is available, but if you notice the profile of the AR brush, it cleans the star, and the large portion of the chamber, but seems to lack the necked in portion of the chamber. For this area, and even other rifle calibers, I suggest using the next caliber (or 2) size up bore brush for cleaning this area of the chamber, and it should NOT be forced down the bore. Using a rigid handle rod, rotating the brush in the same direction going in, and coming out. Afterwards be sure to also lubricate the chamber for corrosion protection.
I always break in/season any new rifle that I purchase. After buying my first Armalite AR10T, I followed the armorers instructions on barrel break in per new owners manual and can testify that the results speak for themselves. The rifle will hit more consistently, period. I have done this dozens of times and it works.It is amazing to me that certain barrels will enjoy certain projectiles, better than others and usually I find it prefers the bullet that was used to season it. This is of course my experience and I can’t say it is the same for others but following the manufacturers recommendations makes sense because, well they’ve put in the time and resources to ensure our success. To me it’s like anything else that’s factory new, you don’t just run out and dog it for fear of mucking it up, common sense. If you’re spending hard earned money on a passion, why not get the most out of it whether it’s a 10-22, or a loaded M1A. Just my experience
Howa published this break in procedure 15-20 years ago. It works very well on stainless barrels and it probably helps on carbon steel barrels but is so tedious that I can’t/won’t do it. After I figured this out, I have resolved to never buying a carbon steel rifle barrel.