THOUGHTS ON BORE FOULING AND CLEANING
Whether we shoot copper jacketed, solid copper or lead bullets that are a few basic facts that are always applicable.
ØAll barrels foul. Regardless if the barrel is manufactured by the hammer forged, broached or button rifled process all barrels will and do foul. Custom made, air gauged, hand lapped barrels are no exception. No matter how a barrel is manufactured there will be microscopic holes in the crystalline structure of the steel. Copper and/or lead will collect in these voids.
ØThe longer the barrel and the faster the rifling twist the more a barrel will tend to foul.
ØChrome molly 4140 – 4142 foul more than 416 stainless.
ØAll types of fouling is not bad. In fact some is good.
There are at least four areas of a bore where fouling can occur.
ØIt is most noticeable in the throat or forcing cone area. Copper or lead fouling in this area is often seen as a lumpy build up that will quickly worsen negatively affecting accuracy.
ØA second area that is readily seen is in inclusion and pit areas of poorly manufactured hammer forged and/or severely corroded barrels.
ØThe third area is on the lands and grooves and is seen as a copper or lead streaking. This is the area that is usually discussed when reference is made to shooting a copper jacketed bullet to clean out the leading.
ØThe forth area of potential fouling is in shallow reamer marks and scratches. Copper and leading in these areas are generally difficult to see without the use of a bore scope and are of no significant import relatively to accuracy provided that the fouling is not allowed to build up. When build-up becomes severe bumps of lead or copper above the bore surface create restrictions that tear the bullet ogive and base as it passes down the length of the barrel. This deforms the bullet and negatively effects consistent bullet flight.
Remember, all barrels foul. It is a simple matter of how many shots are needed to first stabilize velocity then how quickly it fouls so severely that the barrel starts to toss flyers or errant shots. If it takes nearly 10 shots for velocities to stabilize and at that point the barrel is fouled so severely accuracy is impossible you have a problem. The barrel is called a “fouler.” New commercial barrels may foul very badly after only 10 shots. Even new custom made barrels may foul badly after 20 or so. Both can be improved.
“Shooting In the Barrel.” This is how it works – First the barrel needs to be cleaned completely of all copper or lead down to the bare steel. Next shoot a copper jacketed round followed by cleaning with a wet patch of a powder solvent such as Hoppes No.9 to remove the powder residue followed by a dry patch or two so you are down to copper. Next wet patch with an ammonia base copper solvent. Wait a few minutes repeating the step until no copper residue comes out on the patch (usually a blue or green in color). Repeat this process until a single shot produces no copper residue on the first patch. Then go to two shots at a time, then three, etc. The goal is to be able to shoot 10 shots before you get copper deposits from the bore. Once accomplished this should allow at least 15 or more shots before there is sufficient fouling to toss flyers and velocities should stabilize quicker from a cold barrel. This is a time consuming procedure for rifles, much less time consuming for handguns, but the effort will be well worth it. Eventually the barrel will clean with just a few patches and no scrubbing with brushes will be required. It is important to break-in a barrel. The major portion of jacket material or lead must be removed by each successive shot or it will pick-up more fouling and build on itself. It is important, therefore, to get a layer of carbon fouling on the top of the lands and grooves as this hard deposit will prevent copper or lead from stripping from the bullet. This is the good fouling. Why does the break in process work? As already stated there are microscopic holes in the crystalline structure of the steel. Copper and lead collect in the voids. Because like materials tend to attach to one another more and more accumulates until fouling material is higher than the bore surface. This is when accuracy will severely deteriorate and you feel the roughness when a tight patch is pushed through the bore. Copper solvent removes the copper from the voids so each successive shot can slough surface molecules into and over the voids until they are nearly closed. The result is a smoother bore and much less fouling. Note: never use a stainless brush as they do damage the bore. If you find it necessary to use a bronze brush push it entirely through the barrel in one complete motion. Do not pump the brush back and forth. Always use a bore guide for rifles and a muzzle guard for handguns to prevent uneven wear of the rifling forward of the chamber or the crown. Top shooters never pull a metal brush backward through the bore and only use nylon brushes and patches to remove powder fouling. If the barrel is good you should never need to clean it with a metal brush. Obviously if you have a barrel with severe rough spots or tool marks then those areas will not smooth out with the aforementioned procedure. Some advocate that lapping with very fine lapping compound or shooting abrasive jacketed bullets through a thoroughly cleaned bore. I am not a proponent of these methods for various reasons. As it relates to cleaning rods, forget aluminum and uncoated steel. Fouling and dirt attach easily to the surface of aluminum and cause scratches. Spring steel rods can wear on the edges of the lands. Brass, coated steel and carbon fiber are the materials of choice. You should be able to purchase one good rod for handguns and one good rod for riles under .30 caliber and another for .30 caliber plus. With these rods you should be able to attach all loops, jags and brushes with the proper fittings for any caliber guns that you may have.
Can your barrel be too clean? You’re kidding me – right? Nope, if a shooter uses an abrasive type cleaner too often the abrasives can be very effective at removing all traces of powder, carbon and jacket or lead fouling. The abrasives can get the barrel too clean. In effect the shooter is re-breaking in the barrel every time he cleans. This ends up in the dog chasing its tail scenario where the shooter believes his barrel is a fouler because of copper or lead accumulation in the barrel is always present so he works to remove it with more abrasive cleaner but what he does remove is the desirable layer of carbon fouling left by the powder and exposes the bare steel ready to grab lead or copper with the next shot.
Copper fouling – It takes several shots to first heat and then foul a cold clean barrel so velocities stabilize and optimum accuracy is reached. This is because initial shots through a cold clean barrel produce different frictional energy until lube is blown out or laid down and the bore is coated with carbon residue, bullet lube or copper so the bullet friction begins to stabilize. Copper fouling grows! Soft metals gall and stick to similar metal. Each round fired will deposit a little more until accuracy deteriorates. Once a barrel is copper fouled successive shots will not remove the copper. Copper is not easily removed by scrubbing but it is easily removed with a good copper solvent. Ammonia has been the chemical of choice from removing copper from barrels for over 100 years. I have never seen detrimental affects from using an ammonia based cleaner if it is thoroughly removed from the barrel as per the manufacturer’s directions. Here is a link to some excellent test results relative to copper removing solutions
Gun Cleaning Product Tests If you watch a bench rest shooter you will notice that although he or she is probably using a custom high grade barrel he or she does not fire many shots between cleanings as compared to the string of shots most casual shooters fire through their handguns or rifles. This is because accomplished shooters understand that the copper fouling needs to be removed before severe build up happens. They also understand that it is detrimental to remove the protective layer of carbon fouling.
Lead bullets and fouling – The successful use of non jacketed lead bullets involves several factors that are not of normal concern when using jacketed or solid copper bullets. By “successful use” I mean keeping fouling to a minimum and accuracy to an optimum. Recently shooters of lead bullets seem obsessed with the BHN (Brinell Hardness Number) of the lead bullets that they buy or cast. They believe that if they know the hardness of the bullet they can correctly select the right bullet for their particular application. I don’t strictly rely on BHN numbers when selecting bullets because it is only one measured aspect of a cast alloy. Some bullet companies offer published pressure equations that supposedly allow a shooter to determine the amount of hardness needed for a particular load at a known velocity. These equations supposedly show how much pressure is required to make the bullet expand (obdurate) in order for the bullet to fill the lands and grooves. This was important back in the old days of black powder when barrel dimensions varied greatly from one maker to another and even with the same maker. In modern times tolerances have been some- what consistent through the generations of handguns with most of the variation being seen in the cylinder throats. Once you know that dimension for your particular gun then bullet selection for the proper fit is easy. Once you get bullets of a proper fit then obduration no longer becomes necessary to get an effective seal. If the bullet is at or over the largest throat dimension then the bullet will swage down and seal with a perfect fit. The only time this becomes a problem is if the throat dimensions are off by a large margin of more than .002-.003 over the bore dimension. A differential above .003 can cause the bullet to strip within the barrel leaving long stings of leading the length of the barrel.
BHN –vs- Alloy Strength – BHN tells only how hard something is. It tells nothing about alloy strength. You can compare two bullets with the same BHN and one will be more brittle with a higher content of antimony in its composition and very prone to lead fouling while the other will be much stronger, far more ductile and less prone to leading the bore. The standard 2/6 alloy (2% tin, 6% antimony, 92% lead) was not developed for its performance as a cast bullet alloy but because it would pour and run well in automated casting machines. Linotype a 4/12 alloy (4% tin, 12% antimony, 84% lead) is a eutectic alloy meaning that all of the components will melt at the same temperature. In its alloy form it was (I say “was” because it is now almost non existent in the US) too hard for cast bullets except for rifles shooting velocities of 2100 fps. Another alloy is Lyman #2 which is a 5/5 alloy (5% tin, 5% antimony, 90% lead). It is expensive to produce in large quantities and thus expensive to buy. The 1 to 1 ratio produced an alloy that did have a high BHN but is almost as strong as linotype.
The advantages of shooting lead –vs- copper jacketed or solid copper bullets is that most copper bullets run about 35 BHN compared to 21-22 BHN of lead bullets, copper is more abrasive, more difficult to remove and offers no lubrication. Lead is less abrasive than copper by 10 to 1.
Lead fouling - The biggest concern voiced by shooters who are contemplating using lead bullets is the amount of lead fouling that they will have to contend with. Lead fouling is proportionate to the barrel condition, use of proper sized bullets and proper powder. Lead fouling is easier to remove than copper and when correctly loaded with proper size bullets and lube there may be almost no residual lead fouling to clean after shooting hundreds of rounds. Just forward of the throat or forcing cone area, breach bore fouling is found in the 1st ½” or so of the barrel. There is much speculation as to the cause including: constriction of the forcing cone area when the barrel was threaded and crush fitted into the frame, gas cutting causing melted bullet base material, bullets that are too hard or bullets that are too soft. When the bullet first engages the rifling at which point the bullet engraves, the lands act as a cutter that cut through the lead or copper surface. Since the bullet is not ductile it will tend to foul more in this area. Some casters try to overcome this problem with additional lubrication. Many lubes used by bullet makers were selected for their ease of application in the bullet making process rather than their lubrication qualities. A medium hard lube will provide the best lubrication from breech to bore ends of the barrel. Breech bore fouling is most affected and cured by finding the proper powder speed for the particular load. Revolver and pistol shooters used to be limited to just a few powder selections most that were hot and fast and not well suited to lead bullet use. This may well be why Elmer Keith chose 2400 for several of his pet loads. Currently we have many powder choices that offer cooler burning temperatures, better pressure curves and improved cleanliness of powder residue. Barrel fouling in the form of long streaks of lead the length of the barrel from breech to muzzle generally indicate improper bullet fit and improper alloy. Fouling at or near the muzzle end indicates too much velocity or lube that is not performing with the velocity. Following the basic rule that as velocity goes up move down in powder speed often provides a cure. Slower burning powders like Allient 2400, Accurate Arms #9, Winchester WW296, Hodgdon H110 and Little Gun and IMR 4227 seem to work well to achieve magnum velocity without lead fouling. There are several lead remover solutions that work well and the Lewis Lead Remover tool for removing excessive lead build-up. The key with leading as with copper fouling is to keep the fouling to a minimum which will minimize your cleaning efforts.
The subject of barrel break-in, bore fouling, barrel cleaning and lead bullet fitting are controversial subjects upon which even the most learned ballisticians and writers often disagree. The above simply represents my experiences and thoughts on those issues.
To help visualize various bore conditions and what certain fouling looks like, below are several 20X magnified bore photos that were provided as a courtesy from Ken Harrington of the Gradient Lens Corp.
Surface rust
Severe pits in neglected barrel
Pitting in poorly made hammer forged barrel
Fire cracking in leade area
Leading in Throat area
Copper fouling in groove & on edge of land
Copper fouling and damage from steel cleaning rod
Lead fouling on land. Note discoloration of lead from powder residue. No copper present