The Ins and Outs - Rifle

Barrel Wear

When is a barrel shot out? It’s a simple enough question, but one that has many different answers. This answer should depend on the level of accuracy and performance the shooter expects from the firearm. Naturally, the expectations for match competition are going to be higher than one used solely for big game hunting. In the final analysis, the shooter must make this decision.

Certain cartridges are harder on barrels than others, thus greatly affecting the accuracy life. Putting it simply, a barrel is washed out by “X” pounds of powder. Whether it’s spread out over many small charges or a smaller number of large charges, it’s still “X” pounds of powder. For example, a 308 Winchester will have a longer accuracy life than a 300 Weatherby Magnum, simply because it uses less powder per shot.

Heavy loads in intense cartridges (such as the small-bore magnums) will erode the throat of a barrel much faster than milder loads in the same cartridge. Nonetheless, most shooters who purchase the magnums do so for the extra terminal performance they afford, which makes downloading counterproductive. Fortunately, most magnums are hunting rifles that are used to fire relatively few rounds each year. In fact, very few big game hunters do enough firing to wash out a barrel in a full lifetime of active hunting.

In the case of most target rifles and many varmint rifles, a large number of shots may be fired over a short time span. As the barrel heats up from continued firing, so does its susceptibility to erosion and fouling. While this can be controlled when varmint hunting, rapid fire and long strings of sustained fire are part of the game for the competitive high-power shooter. Since the shooter can’t control this, he needs to recognize it as a potential problem and deal with it accordingly. Cleanings will need to be both more frequent, and thorough, to prevent fouling from getting a foothold. With the increased cleanings, proper cleaning technique becomes essential to avoid damage caused by the cleaning itself. Even with proper cleaning technique, many target shooters go through a new barrel every season.

Components

The reloading components available to today’s handloader are the finest the sport has ever known. Modern powders are much less erosive than those used by past generations of reloaders. Bullets are now jacketed with gilding metal alloys that don’t foul bores nearly as badly as the older cupronickle jackets did. Primers, however, are undoubtedly the single biggest improvement for extending barrel life. While most handloaders have heard primers referred to as “non-mercuric” and/or “non-corrosive,” few (who have been shooting less than 50 or 60 years) have a real understanding of what these terms really mean.

Corrosive primers used potassium chlorate as the oxidizer in the priming compound. When ignited, the potassium chlorate produces potassium chloride, a compound very similar to common table salt. Like any salt, it would attract and hold moisture. This moisture, in turn, would very easily cause rusting. The old frontiersmen had a saying, “the sun must not set on a dirty gun.” This was a direct reference to the absolute necessity of cleaning a gun almost immediately after firing it, to avoid a corrosion problem. Leaving it for a few days simply was not an option. Once potassium chlorate was identified as the cause in the corrosion problem, it was replaced, leaving us with the “non-corrosive” primers we enjoy today.

Fulminate of mercury was one of the more popular initiators used in early primers. When jacketed bullets and smokeless powders became widely accepted near the turn of the century, operating pressures increased drastically for the average cartridge. With these new higher pressures, handloaders soon found that cases frequently became extremely brittle after the first firing, rendering them useless for further reloading.

The culprit behind this was the mercury in the primer. Upon firing, the mercury amalgamated with the brass case and chemically attacked it, causing it to become brittle. Primers made without fulminate of mercury eliminated this problem. These primers are referred to as being “non-mercuric.” While not specifically a problem as far as bore erosion is concerned, mercuric primers are discussed here because of their close association with corrosive primers. Today, virtually all U.S. made ammunition and component primers are non-mercuric and non-corrosive. Corrosive and/or mercuric primers may still be encountered in surplus military ammunition, especially foreign types manufactured prior to WWII, and surplus ammunition from former Warsaw Pact countries.

Erosion from Propellants

With the passing of corrosive primers, erosion from the propellant itself is undoubtedly your barrel’s greatest enemy. When the powder is ignited, it creates extremely hot gases under tremendous pressure. These two factors combine to create erosion, particularly in the throat area of the barrel.

Some older powders, such as DG Pyro or Hi-Vel#2, were very erosive due to their high nitroglycerine content and the resulting high flame temperature. When the 1903 Springfield was first introduced, the original loading of a 220 grain round-nose bullet at 2200 fps gave a useful barrel life of only 800 rounds. This was due to the high nitroglycerine content and resulting high flame temperatures of the powders then in use. As powder chemistry has improved, longer barrel life has been achieved. However, erosion from propellants will probably remain the No. 1 factor in barrel wear in the foreseeable future. This situation is unlikely to change until some radical improvements are made in the chemical makeup of the powder.

Some debate has ensued over the merits of ball powders vs. extruded tubular powders. Extensive testing at Lake City Ammunition Plant found “no significant difference in bore life, accuracy wise, when using either IMR propellants (extruded tubular) or spherical propellants (ball powder).” While these comments were made specifically about the 30 caliber and 7.62mm NATO Match ammunition, the same situation will hold true for most other cartridges.

Improper Cleaning

It is a sad fact that with the great improvements in better barrel steels, non-corrosive primers, and less erosive propellants, probably as many of today’s barrels are ruined by improper cleaning as by neglect. Careless use of a cleaning rod, failure to use bore or muzzle guides, improper use of harsh solvents, or the use of poor quality or badly maintained cleaning equipment all can do more harm to a firearm than no cleaning at all. This need not be the case, and the few minutes it takes to learn proper cleaning techniques is time well spent. There are several specific types of fouling, each with its own set of problems, which need to be addressed separately.

Metal Fouling

Metal fouling may refer to either lead or copper buildup within the bore. This fouling is the result of the friction, pressure and high temperatures inherent in firing. Guns will vary a great deal in their tendency to foul, depending on such factors as the smoothness of the bore, the fit between the bullet and bore, jacket hardness and intensity of the load.

Copper fouling is normally seen as a copper “wash,” sometimes plainly visible on the surface of the bore. Despite its rather innocuous appearance, this fouling can seriously degrade a barrel’s accuracy potential. While removing this fouling can be tedious, it must be done to maintain top accuracy.

Fortunately, today’s shooters have perhaps the best assortment of truly effective copper solvents ever available.

Lead fouling, also called “leading,” is usually much more noticeable, frequently as a lumpy buildup at the throat or forcing-cone area of the barrel. Being an extremely soft metal, lead is seriously affected by the stresses of high-intensity loads. Unless very well cast from a suitably hard alloy and lubed with an effective lubricant, lead bullets are best reserved for lower pressure loads and reduced velocities. Once leading has begun, successive bullets passing over a spot in the bore already affected by these deposits will worsen the condition rapidly. This, in turn, will cause an immediate and sometimes serious loss of accuracy unless removed.

Powder Fouling

Powder fouling is the result of the combustion of the powder that leaves an ash, or residue, in the barrel. In extreme cases, it may take the form of a carbon buildup. Powder fouling can generally be removed without too much difficulty by the milder solvents and a good scrubbing with a bronze brush.

Bullet Friction

Bullet friction, as it pertains to barrel wear, is frequently a topic of discussion among shooters. While this friction causes some wear, it is the least measurable factor in barrel life. In Small Arms Design Vol. II, Col. Townsend Whelen mentions a Springfield 22 rimfire barrel that had been gauged when it was installed, and again after having fired in excess of 80,000 rounds. A uniform wear of .0004” was observed throughout the length of the bore, undoubtedly caused by bullet friction. Granted, this was referring to lead bullets, not jacketed. However, when we consider that most centerfire barrels are completely shot out due to throat erosion in less than 10,000 rounds, bullet friction becomes utterly meaningless as a factor in barrel wear.

There is perhaps one situation where bullet wear may pose a problem —poorly made lead bullets, cast from dirty material. If the dirt and grit commonly found on used wheel weights and other sources of scrap lead is not removed by frequent and thorough fluxing, it will be cast into the bullets. Any grit exposed on the bullet’s bearing surface will act as an abrasive lap. This situation is easily preventable, simply by using some common sense and good casting techniques.

Proper Records

The simple answer to these problems is to maintain a logbook for each firearm. This may be a small logbook specifically designed for the purpose, such as those marketed by Creedmoor Armory, or simply a 3" X 5" note pad found in any business supply or stationery store. The notations need not be extensive: date, number of rounds fired, and perhaps the type of firing (match, load development, hunting, etc.) is sufficient.

You may also wish to note the type of cleaning technique used, especially if you are doing something other than your normal routine. This is perhaps the best way to make valid conclusions as to the various types of bore cleaners available, and the best ways to use them. This also helps in spotting any developing trends in a particular barrel regarding changes in fouling patterns. These changes can help alert the shooter to a problem with the bore, be it erosion, etching or other physical damage.

Perhaps the best reason to maintain an accurate logbook is that it might save you the cost of a barrel. If you have a barrel whose accuracy has noticeably deteriorated, yet the logbook reveals a relatively small number of rounds fired through it, the bore probably isn’t shot out. In these cases, the problem might be resolved by a more thorough cleaning, perhaps using stronger methods than previously used. If the barrel isn’t fouled, and the logbook tells you that it should not be shot out yet, the problem may be in the bedding, the scope, the crown, your loads, etc.

Most shooters tend to badly overestimate the number of rounds they’ve fired through a particular barrel, leading to the premature conclusion that the bore is shot out. Many of the “shot out” barrels that are replaced these days could be completely restored by a good cleaning. At around $350 for threading, chambering and installation of a good quality barrel, this is no small consideration.