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Gunsmithing Information

Barrel Cleaning and Break-In


From: Sinclair Precision Reloading Handbook, 7th Edition
Used by permission of Sinclair International, Inc.


"Shooters are beginning to realize that old wives' tales about the lack of need for cleaning today's rifles, because of modern primers and powders, are just that-- tales. Only proper and regular cleaning will keep your rifle at it's peak accuracy potential.


All one has to do is visualize what happens once we pull the trigger on that first round. The bullet from the first round, fired through a new barrel, leaves a deposit of bullet jacket material in the bore, and on top of this is left the residue from the burnt powder. The second round fired, will deposit another layer of jacket material over the powder residue and at the same time compress this residue between two layers of jacket material. This sequence occurs with each round fired.


Bear in mind, this compression is severe at 45,000 PSI or more, and at temperatures that are beyond your wildest dreams. After 12 to 15 rounds fired, this sequence of events will become detrimental to your rifle's accuracy.


There's no getting around the fact that proper cleaning is all important to accuracy. Competitive shooters think nothing about spending $200 plus for a quality match grade barrel because they know that the mark of a good quality rifle barrel is one that has a bore of uniform diameter from one end to the other. (Normally this tolerance is .0001" on match grade barrels.) If allowed, due to improper cleaning, fouling will actually build up in the rifling grooves and give the appearance that the barrel is "shot out".


The groove depth on center fire rifle barrels is normally less than .005" deep, so if you stop and think about it, there just isn't much room for the fouling.

The build up will start in the corners of the groove and gradually build out to the center. Only a good solvent and a tight brush will clean out the fouling.

We can honestly say that over the years, we have seen more "shot out" barrels that were loaded up with fouling than were actually "shot out".

We seriously doubt it is possible to get a barrel 100% clean, but the closer we get, the more we will benefit. If we fire 10 rounds through a barrel and out cleaning procedure is only adequate enough to remove 8 or 9 rounds of fouling, it is easy to visualize what happens after we fire 500 rounds.


Most of the barrels we have worked with are new, match grade stainless steel, barrels known for their fine accuracy potential and close manufacturing tolerances. Although we're unable to point to a single solvent as "the best", all of out experimentation with solvents and cleaning techniques has firmly convinced us that each new barrel MUST go through a "break-in" period prior to actually being put to work. While the temptation to see how that expensive new barrel will group is a great one, our best--and only--advice is DON'T DO IT.


The break-in method--conditioning, if you will--which has proven successful for us is to fire only three rounds between cleanings for the first 30 rounds, and then fire only five rounds between cleaning for the next 100 rounds. The barrel should then be fired no more than 20 rounds between cleanings, preferably less. Bench rest shooters generally clean their rifles after every 6 to 10 rounds. for those seeking to obtain the best possible accuracy form a favorite hunting or varmint rifle, there is a lesson to be learned here!


The break-in method we've outlined above is tedious, but it does pay dividends in the long run. We've checked out the results "on the target" and with a bore scope, and we're convinced that lesser cleaning techniques result only in fouled barrels and impaired accuracy. we've followed the procedure outlined above with Shooter's Choice and with Mercury Quicksilver Engine cleaner with uniformly excellent results.


We have experimented at length with various cleaning solvent and techniques and the only hard and fast rule we've proven to ourselves is that no one cleaning method or solvent is the so called "final answer" to getting rifle bores clean.


We prefer a coated cleaning rod over steel rods, and feel they are safer to use for a couple reasons.


A steel rod, unless it is just a few thousands under bore size, will flex while being used, and this flexing actually creates a tapping or peening condition in the bore which will damage the lands of the barrel. Also, after repeated use you will notice that the rod will show signs of the rifling twist on the outside diameter of the rod.

The so called "bore size" cleaning rods can really destroy a barrel should the patch not be centered, or should the patch unravel and get wedged between the rod and rifle bore. Such conditions cause the rod to swage itself against the rifle bore, and galling occurs.


If the steel rod has a bow, or gets a slight bend in it, these conditions become even worse, whereas a bow in a coated rod won't do any damage.

Coated rods prevent the above mentioned problems, plus they are easier to keep clean. The coatings are more fragile, of course, but I would rather ruin a $20.00 cleaning rod than a $200 barrel.


Our preference in cleaning rod jags is the type that stab the patch rather than wrap around the jag or slip through the jag. The term "cleaning patch" is misleading. Patches don't clean, they are used to carry the solvent into the bore and to carry the "crud" out. This is the reason we prefer the stab type patch jag, stab it, push it through the bore and let it fall off the jag as it exits the muzzle. It's job is done, no need to drag dirty patches back and forth through your rifle fore.

Regardless of your preference in rods, be sure they are of one piece construction and always wipe off the rod's exterior prior to pushing it through the bore.

The actual cleaning procedure will vary from shooter to shooter but we have found the following quite successful. ALWAYS USE A BORE GUIDE TO PROTECT THE BARREL'S THROAT


  1. Push a patch wet with Shooter's choice or Quicksilver through the bore to remove any loose powder ash. No need to have the loose stuff get into your brush to be dragged back and forth while brushing.
  2. Wet a brush with solvent and make eight or ten passes through the barrel. Repeat with a second application.
  3. Push two or three wet patches through the bore to remove the residue and allow the solvent to soak in the bore for 10 to 20 minutes.
  4. Push two or three dry patches through the bore before firing.
  5. Wipe out the chamber using a large patch on the end of your cleaning rod or use our action cleaning tool swab and you're ready to go again.


After four or six normal cleaning in this fashion--or should you encounter a barrel which copper fouls badly, it is a good idea to use a good copper solvent. Sweets 7.62 is the best we have found.


Sweets 7.62 should be used on a patch or a cotton mop as it will "eat a brush alive". We suspect that a bore mop has the ability to "carry" more of the solvent into the bore and may be better suited for this operation. they can also be cleaned out with hot water, dried and re-used.


Apply the Sweets 7.62 solvent to the bore, swabbing back and forth as you do, let it set and work for 10-15 minutes and then push a patch through the bore, If the patch comes out with a green color jut repeat the operation until patches come out clean. DO NOT LEAVE SWEETS IN THE BORE FOR MORE THAN 20 MINUTES AT A TIME!


Quicksilver and Sweets 7.62 do not contain rust preventatives, al always follow up with a solvent that does, like Shooter's Choice.


A word of caution, any cleaning solvent that is going to do a proper job cleaning can be potentially harmful to the user so don't take a bath in it.

After cleaning the bore it is a good idea, ever so often to clean out the bolt locking lug area and the bolt face."


In addition to the above material from Sinclair, there are some additional procedures which I have found useful. I normally use a bore brush one size larger when cleaning heavily fouled barrels. I like the "roll jag" better than the spear pointed jag, feeling that its cleaning action is superior. I also use a good quality gun oil in the bore after cleaning rather than leaving a solvent in the bore. In very damp climates I use a light coat of RIG in the bore and clean it before firing.


Anyone interested in accurate rifles should obtain a current copy of Sinclair's Precision Reloading Manual and a copy of their current catalog.


Quality cleaning products are available from:


Sinclair International, Inc.
2330 Wayne Haven Street
Fort Wayne, Indiana 46803

Brownells, Inc.
Route 2, Box 1
Montezuma, Iowa 50171


By following the above procedures you can keep you rifle shooting accurately for many thousands of rounds. Remember that rapid fire shooting wears a barrel much more quickly than slow fire. Unless you are practicing rapid fire for DCM competition, do not overheat your barrel. By using the above break-in and cleaning procedures, I have seen very notable decrease in jacket fouling.


I have been testing the Outer's "Foul-Out II" for the last few months. It has proven very effective in cleaning heavily fouled barrels. It MAY be possible to take a heavily fouled barrel or one that has not followed the above break in procedure, clean it fully with the Foul-Out II and then use the above break in procedures to reduce future fouling. One recent test I preformed used a barrel broken in using the above procedure and a brand new (unfired) barrel and firing nine rounds then comparing the amount of fouling build up. The results- the new barrel was heavily fouled, while the properly broken in barrel showed no visible jacket fouling. When cleaned with Hoppe's No. 9 and allowed to set for 1/2 hour with solvent in the bore, the drying patch with the unfired barrel showed extensive green discoloration, the normal indication of jacket fouling. The broken in barrel's drying patch showed no trace of green discoloration. Clearly, a properly broken in barrel will stay unfouled longer. Whether a barrel, never properly broken in, can be fully cleaned and then broken in is currently under examination. If it can, many older barrels can be restored.


A final reminder. Powder solvents (Hoppe's No.9, Marksman's Choice, etc) are mainly aimed at removing powder residue. Jacket fouling solvents (Sweet's 7.62 and Outer's Cop-out for their Foul Out system) do not work on powder residue. Both jacket and powder fouling is built up in layers on top of each other. You must use both types of solvents to fully clean your rifle barrel, especially if it was never properly broken in. Good shooting.


The foregoing material is copyrighted by L. Bengtson Arms Company, 1995, and Sinclair International. Sinclair International material is used with permission of the copyright holder with our appreciation.


Copyright © 1995 by L. Bengtson Arms Co. and Sinclair International, Inc.