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.
LONG & SHORT TERM STORAGE:
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.
BREAK-IN & CLEANING:
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.