What is the best way to break-in and clean a Barrel?


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Below are our recommendations for proper break in and cleaning of a barrel. The information below is meant as a guideline and not meant as step by step instructions. If you have a better way that works for you without damaging the bore or using improper chemicals, by all means continue to use your methods. Many successful competitive shooters will use these instructions to the letter, some will disagree.


Your Krieger barrel has been shipped to you with a SHORT TERM rust inhibitor sprayed in the bore to protect it from corrosion during shipping. Upon receipt of your barrel, you should first review the order confirmation and/or packing list to make sure the barrel matches the specifications you ordered. The very next thing you should do is clean the bore and apply a bore protectant suitable for the length of time it will be stored. This can range from a light gun oil all the way up to a preservative grease or cosmoline. The same should be done after a barrel is fit to your rifle. 

Preventing oxidation/corrosion in the barrel is the responsibility of the customer. We cannot be responsible for a barrel that has been improperly stored, neglected, or abused by either the end customer, gunsmith, or a distributor.


With any premium barrel that has been finish lapped -- such as your Krieger Barrel --, the lay or direction of the finish is in the direction of the bullet travel, so fouling is minimal compared to a barrel with internal tooling marks. This is true of any properly finish-lapped barrel regardless of how it is rifled. If it is not finish-lapped, there will be reamer marks left in the bore that are directly across the direction of the bullet travel. This occurs even in a button-rifled barrel as the button cannot completely iron out these reamer marks.

Because the lay of the finish is in the direction of the bullet travel, very little is done to the bore during break-in, but the throat is another story. When your barrel is chambered, by necessity there are reamer marks left in the throat that are across the lands, i.e. across the direction of the bullet travel. In a new barrel they are very distinct; much like the teeth on a very fine file. 

When the bullet is forced into the throat, copper dust is removed from the jacket material and released into the gas which at this temperature and pressure is actually a plasma. The copper dust is vaporized in this plasma and is carried down the barrel. As the gas expands and cools, the copper comes 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 is actually for the most part the new throat.

If this copper is allowed to stay in the bore, and subsequent bullets and deposits are fired over it, copper which adheres well to itself, will build up quickly and may be 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 will vary slightly in how many rounds they take to break in For example a chrome moly barrel may take longer to break in than stainless steel because it is more abrasion resistant even though it is a similar hardness. Also chrome moly has a little 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. Rim Fire barrels can take an extremely long time to break in, sometimes requiring several hundred rounds or more. But cleaning can be lengthened to every 25-50 rounds. The break-in procedure and the cleaning procedure are really the same except for the frequency. Remember the goal is to get or keep the barrel clean while breaking in the throat with bullets being fired over it.

Finally, the best way to tell if the barrel is broken in is to observe the patches; i.e. when the fouling is reduced. This is better than some set number of cycles of shoot and clean as many owners report practically no fouling after the first few shots, and more break-in would be pointless. Conversely, if more is required, a set number would not address that either. Besides, cleaning is not a completely benign procedure so it should be done carefully and no more than necessary.


This section on cleaning is not intended to be a detailed instruction, but rather to point out a few do's and don'ts. Instructions furnished with bore cleaners, equipment, etc. should be followed unless they would conflict with these do's and don'ts. 

You should use a good quality one piece coated cleaning rod with a freely rotating handle and a rod guide that fits both your receiver raceway and the rod snugly. How straight and how snug? The object is to make sure the rod cannot touch the bore. With M14/M1 Garand barrels a good rod and muzzle guide set-up is especially important as all the cleaning must be done from the muzzle. Even slight damage to the barrel crown is extremely detrimental to accuracy.

There are two basic types of bore cleaners, chemical and abrasive. The chemical cleaners are usually a blend of various ingredients including oils, solvents, and ammonia (in copper solvents). The abrasive cleaners generally contain no chemical solvents and are an oil, wax, or grease base with an extremely fine abrasive such as chalk, clay, or gypsum.

We recommend the use of good quality, name brand chemical cleaners on a proper fitting patch/jag combination for your particular bore size and good quality properly sized nylon or bronze brushes. 

So what is the proper way to use them? First, not all chemical cleaners are compatible with each other. Some, when used together can cause severe pitting of the barrel, even stainless steel barrels. It is fine to use two different cleaners as long as you completely dry the bore of the first cleaner from the barrel before cleaning with the second. And, of course, never mix them in the same bottle. NOTE: Some copper solvents contain a high percentage of ammonia. This makes them a great copper solvent, but if left in the bore too long, can damage/corrode the steel. Do not leave these chemicals in a bore any longer than 10-15 minutes MAXIMUM! DO NOT EVER use straight ammonia to clean a barrel.

Follow instructions on the bottle as far as soak time, etc. Always clean from the breech whenever possible, pushing the patch up to the muzzle and then back without completely exiting the muzzle. If you exit the muzzle, the rod is going to touch the bore and be dragged back in across the crown followed by the patch or brush. Try to avoid dragging items in and out of the muzzle, it will eventually cause uneven wear of the crown. Accuracy will suffer and this can lead you to believe the barrel is shot out, when in fact, it still may have a lot of serviceable life left. A barrel with a worn or damaged crown can be re-crowned and accuracy will usually return. Have the crown checked by a competent gunsmith before giving up on a barrel that may otherwise be in good condition.

This information is intended to touch on the critical areas of break-in and cleaning and is not intended as a complete, step-by-step guide or recommendation of any product. Use a quality one piece cleaning rod that is either vinyl coated or carbon fiber, a rod guide proper for the action you are cleaning, and chemicals, jags, patches, and brushes that you have determined work best for you. There is no right answer to cleaning products and equipment, however under no circumstances should you use a stainless brush. If you choose to use brushes in your cleaning use only quality bronze phosphor brushes or nylon. Clean them after every use to extend their life. Copper solvents will dissolve a bronze brush rather quickly.


The following is a guide to break-in based on our experience. This is not a hard and fast rule, only a guide. Some barrel, chamber, bullet, primer, powder, pressure, velocity etc. combinations may require more cycles some less. It is a good idea to just observe what the barrel is telling you with its fouling pattern and the patches. But once it is broken in, there is no need to continue breaking it in.

Initially you should perform the shoot-one-shot-and-clean cycle for five shots. If fouling hasn't reduced, fire five more cycles and so on until fouling begins to drop off. At that point shoot three shots before cleaning and observe. If fouling is reduced, fire five shots before cleaning. Do not be alarmed if your seating depth gets longer during break in. This is typical of the “high spots in the throat being knocked down during this procedure. It is not uncommon for throat length to grow .005-.030 from a fresh unfired chamber during break in.


  1. 5-10 one-shot cycles
  2. 1 three-shot cycle
  3. 1 five-shot cycle

Chrome moly

  1. 5 - 25 - one-shot cycles
  2. 2 - three-shot cycles
  3. 1 - five-shot cycle


Quite often we get asked about the service life of a barrel or How long will my barrel last?. The truth is a complicated result of many factors, ultimately service life is determined by a combination of cartridge, cleaning practices, shooting style, etc. A barrel is “Shot Out or at the end of its service life when the throat erosion has resulted in the bullet no longer able to be seated to touch the lands and still remain in the case by a reasonable amount, and heat checking/cracking has progressed several inches forward of the throat. 

These are the normal determining factors that cause a degradation in accuracy from when the barrel was ‘fresh or new. Cartridge choice, powder selection, pressure (a combination of powder selection/amount, bullet weight, and cartridge design), and cleaning procedures will ALL have an effect on how long of a service life your particular barrel has. No two pieces of barrel steel will have the same exact properties either. We can give an “average barrel life for a particular cartridge if it is a common one used in competition, but that is no guarantee of any round count due to all of the listed factors above. Most cartridge designs larger than .223 Rem or .308 Win in powder capacity to bore ratio will begin to erode the throat measurably in less than 1000 rounds.

Thank you for choosing a Krieger barrel.