When is a barrel shot out? Its 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
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 its spread out over many small charges or a smaller
number of large charges, its 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
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 cant 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.
The reloading components available to
todays 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 dont 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 barrels
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.
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 todays 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 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 barrels accuracy potential. While removing
this fouling can be tedious, it must be done to maintain top accuracy.
Fortunately, todays shooters have
perhaps the best assortment of truly effective copper solvents ever
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
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, 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 bullets bearing surface will act as an abrasive
lap. This situation is easily preventable, simply by using some
common sense and good casting techniques.
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 isnt 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 isnt
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
Most shooters tend to badly overestimate
the number of rounds theyve 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.