Brass Basics: Case Selection and Prep

CASE CLEANING

Vibrator/tumbler case cleaners use ground corn cobs or ground walnut shells to clean cases through abrasive action. This is probably the best system for cleaning large numbers of cases.
Vibrator/tumbler case cleaners use ground corn cobs or ground walnut shells to clean cases through abrasive action. This is probably the best system for cleaning large numbers of cases.

Most shooters like to keep their cases shiny and bright. They look better and are easier to find on the ground. Shined cases are less likely to collect dirt and grit and can be easily checked for damage caused by corrosion. Dark cases hide flaws that may run deep.

There are two basic methods of case cleaning. The first is wet cleaning. This uses a concentrated, acid-based cleaner that is mixed with water. This must be done in a glass, plastic or stainless-steel pan. Warming the pan, with the cases in the mixture, on the stove speeds the process. The cleaned cases must be rinsed to remove all residue and oven dried on “warm.” Too much heat can ruin the heat treatment of the cases. Cases should be decapped before wet cleaning.

Dry cleaning is tumbling the cases in an abrasive cleaning media made of ground corn cobs or ground walnut shells. This requires a motor-driven tumbler or spinner-type tool into which the cases and media are put for cleaning. The cleaned cases must be wiped free of dust, and any media trapped inside must be removed.

CARTRIDGE CASE & AMMUNITION STORAGE

“Store in a cool dry place” is good advice for keeping about anything, but this isn’t always possible. Depending on one’s paranoia and/or notion of thrift, the decision may be made to buy a large quantity of cases. Sometimes quantity simply accumulates in the form of various loadings, always expanding with the addition of new guns to a shooting battery. Ultimately the questions arise: how long will this stuff last (both cases and finished ammunition) and how do I take care of it?

In answer to question one, the shelf life of modern ammunition (both commercial and good handloads) is virtually indefinite if kept under ideal conditions — sealed, cool and dry. Most of us don’t have this kind of storage. Experts have preached since time immemorial the avoidance of heat and damp when storing. Actually, heat and damp by themselves don’t do all that much damage to quality ammunition. Heat does drive off volatiles in lubricants and exposed propellent-powders and to a degree accelerates decomposition in smokeless powders.

Liquid case cleaners contain a mild acid and require no more equipment than a stainless steel, plastic or glass pan to soak them in. Cases should be decapped before cleaning and either air-dried or oven-dried at no more than 150 degrees F.
Liquid case cleaners contain a mild acid and require no more equipment than a stainless steel, plastic or glass pan to soak them in. Cases should be decapped before cleaning and either air-dried or oven-dried at no more than 150 degrees F.

Heat and damp together are most injurious because water absorbs pollutants and heat accelerates chemical reactions between these pollutants and ammunition. The triple threat in airborne pollution consists of acids, ammonia, and sulfur compounds. All occur naturally in the atmosphere in addition to being man-made pollutants. They are also found in a variety of household products. Salts, through direct contamination, are a fourth hazard. Pinpointing the exact reason why a particular batch of ammunition went bad is a mystery to be solved by an expert metallurgist-detective through chemical analysis and examination of cartridge surfaces with a scanning electron microscope.

I have often heard it said that certain metals “crystalize” and become brittle with age. I put this question to Professor Bryan Wilde – a metallurgist and director of the Fontana Corrosion Center at The Ohio State University. He assured me this was not the case. Cartridge brass has a crystalline structure.

When exposed to pollutants in the atmosphere, notably ammonia, a breakdown of the alloy begins as ammonia dissolves the copper. Acids in the atmosphere dissolve the zinc in a process known as “dezincification.” In areas where the metal is stressed – case necks, shoulders and crimps – the crystal edges are farther apart, thus speeding the breakdown in a process known as “season cracking.”

Season cracking begins as tarnish, gradually turning into deep corrosion which often follows the edges of the crystals, giving the surface a frosted appearance, leading to the impression the metal is changing its structure. This phenomenon was first recorded in nineteenth-century ammunition used by the British in India, where it was exposed to the ammonia-rich fumes of cow dung and urine in a hot, humid climate.

Salts occur in perspiration and are a problem mainly because they are hygroscopic – they draw and hold water which combines with the salt to corrode metals the wet salt mixture contacts. Sulfur, notably sulfur dioxide (SO2), causes a tarnish when it combines with lead and copper to form sulfides. When SO2 combines with water (H2O) the result is sulfurous acid (H2SO3). Lead and lead alloy bullets are subject to damage mainly from acids. These attack lead, causing a hard white crust to form. If the bullet can be hand-turned in the case there is not a hermetically tight seal and sooner or later moisture will enter.

Manufacturers continue to come up with better priming, powder, lubricants, case materials, sealants, and packaging. What you buy represents the manufacturer’s state of the art combined with his sense of economy at the time the product was made.

Plating cases with nickel and plating or jacketing bullets with copper inhibits corrosion by acid. Non-hygroscopic bullet lubricants keep moisture away from bullets and out of case interiors. Paper boxes absorb moisture but are no problem if kept dry. Those that contain high levels of acid residues should be disposed of and the cartridges repacked in plastic boxes which are chemically inert and if sealed, keep most moisture out. Therefore, if the cases/ammunition are in good shape when stored, and if kept dry and cool, they will remain in good condition for decades.

Plastic boxes are best for ammunition storage and come complete with information cards.

A second problem that still crops up is brittle brass. After cartridge brass is formed it gets a final heat treatment called “stress relief.” This process involves less heat than annealing and is done to bring the brass to the optimum degree of springiness. Occasionally a batch will get through that is improperly treated.

It will perform fine when new, but after ten or more years, the brass will have returned to its original brittle state. This is exacerbated by the process of firing and resizing. Cases will split and sometimes burst. Any corrosion taking place will hasten this process. One advantage of the old gilding-metal cases is that they were less subject to corrosion and stress changes because they were softer.

Beyond cool and dry there isn’t much to be added regarding shelf-storage. For the longest run, the best means is a military ammunition can with a rubber gasket along with a fresh packet of desiccant, closed on a dry day and opened as infrequently as possible. If ammunition is stored in a can or tightly sealed cardboard container, don’t break the seals (letting in pollutants) to have a look.

Second-floor rooms are perhaps the best for shelf-stored ammunition, avoiding attic heat and basement damp. Cartridges should be stored away from cleaning products containing ammonia, bleaches, or acids. If it must be stored in a basement, run a dehumidifier and keep ammunition off the floor. It is a good idea to make timely checks of shelf-stored cartridges in non-sealed boxes – twice a year is fine – to inspect for case tarnish or a haze of white corrosion forming on lead bullets.

To the above might be added a list of dumb things not to do. Slathering a gun with Hoppe’s No. 9 may do well to keep it from rust, but if this is the one kept for home defense the ammonia in No. 9 spreading onto the cartridges therein will eat right into them. The same is true for any ammonia-bearing solvent cleaner. A rust inhibitor such as WD-40 spray may work preservative magic, but WD-40 is designed to penetrate and will do so in the seams between primers and cases, eventually working into the priming compound and neutralizing it. Leaving cartridges in leather belt loops may look nifty, but if the leather has residual salts or acids in it these will eat into the metal, etching a ring which adds nothing to the looks or strength of the cartridge case.

Lastly, it should not be forgotten that cartridges are interesting. People can’t keep their sweaty hands off them. Ask any collector how often he wipes down his collection after “showing” it to friends. Two suggestions passed to me by collectors are treating specimens with a light coat of rust inhibiting grease or liquid car wax of the Rain-Dance variety as the best defense against repeated attacks of finger-borne corrosion. Like the guy at the gas station used to say: “Rust never sleeps.”

This article is an excerpt from the ABCs of Reloading, 9th Edition, due for release Fall 2010. Be sure to check GunDigestStore.com new releases to get your copy.

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