Cartridge Naming Systems

In North America, there is no defined, universally accepted cartridge naming system. Cartridge naming has been commercially driven and naming is typically determined by the original manufacturer.

In Europe, cartridge naming systems are controlled by government agencies and the systems are adhered to by all manufacturers.

Naming systems are varied and covered extensively in Cartridges of the World .

Case Design

The basic shape of the cartridge case is linked to firearms evolution and development. Most early cartridge cases were straight walled, which was the optimum shape for use with black powder. Protruding rims at the rear positioned the case in the chamber and provided the support needed to prevent the firing pin blow from driving the case deeper into the chamber. The rim also allowed the extractor to grasp and withdraw a fired case from the chamber. This design was successful for single-shot arms, shotguns, and repeating arms with tubular magazines.

Eliminating the protruding rim was key to box magazine success. The simpler box magazine was less expensive to produce because the complex feed parts (required in tubular magazines) were eliminated.

Removing the rim required that

• the case provide positive support for proper positioning,
• the case resist the firing pin blow,
• some gripping surface be provided for the extractor.

Getting the required positive support relied on other features of the case. Some straight-wall or straight-taper cases (e.g., .30 U.S. Carbine,
.45 Auto) use the case mouth to support the cartridge. Larger cartridges were bottlenecked and the sloping shoulder became the support point. Some bottlenecked cases did not have enough shoulder for support. In another variation, the British firm of Holland & Holland developed the belted case; a small ring placed forward of the extractor groove supported the case.

The gripping surface was provided by designing a rimless case. Although the rim is present, it does not protrude beyond the body of the case. The extractor groove is an undercut made in the solid portion of the case in front of the rim.

 

Primer Evolution

Primers are devices that, when sharply struck, burn or explode to provide the heat source required to ignite the propellant charge. All modern small arms primers are chemical initiators.

 

Primers

• provide an initial spark or flame,
• establish the preignition pressure for the main charge,
• provide a gas seal for the cartridge.

For decades, mercury fulminate was the most commonly used primer. Although contemporary with fulminating powders containing potassium chlorate (whose residues promoted rust), mercuric priming was preferred because it did not rust the gunmetal.

When brass cartridges were adopted for use, it became apparent that mercuric residues (when in contact with brass), resulted in brittle cartridge cases. Such cartridges were fine for the first firing but could not be safely reloaded. The brittle brass could fail the next time it was fired, releasing hot gases. Thus, mercuric priming was replaced with chlorate priming. The U.S. military arsenals abandoned mercuric priming in 1898 at the beginning of the smokeless powder era.

Smokeless Primers

In the 1920s, lead styphnate was used as an initiating compound because it did not produce corrosive residues. Many other mixtures were tried and some were released for market trials. The combination of materials that worked best was a blend of lead styphnate, antimony sulfide (fuel), and barium nitrate (oxidizer). By the 1930s, all U.S.-made commercial primers were using this basic formula.

Styphnate priming compounds may contain other materials in addition to the three main compounds, such as the following:

• Sensitizer - makes the material more shock sensitive. The most prevalent sensitizer is tetracene.
• Finely powdered aluminum - added fuel used to project incandescent particles into the propellant.
• Organic binder - keeps the dried primer pellet consolidated, e.g., gum acacia.
• Dye - facilitates visual inspection of primers during manufacturing.

A Boxer primer used for a rifle or handgun has a minimum of three components: the metal cup, the priming compound, and the anvil. Many have an additional componenta thin paper cover between the compound and the anvil. This is known in the industry as the foil paper because original percussion caps had a layer of foil over the mixture for protection.

Shotshell primers are more complex. Because the shotshell case is largely nonmetallic, an extra part, the battery cup, is added to better support the anvil and resist operating pressures. In addition, the large flash hole has a paper or thin plastic cover, a relatively recent feature.

The lead styphnate percussion primer has remained nearly unchanged in form or chemistry since the 1930s. The discharge residue of these primers contains lead oxides and nitrates. Recent concerns over airborne lead in poorly ventilated indoor ranges have led to the investigation of lead-free primers and toxic metal-free primers. Future primer development will undoubtedly focus on additional improvements to low-toxicity compounds.

Selected Bibliography

The Selected Bibliography is a list of the writings that have been used in the assemblage of the training program and is not a complete record of all the works and sources consulted. It is a compilation of the substance and range of readings and extensive experience of the subject matter experts.

1. Ball, P., and D. Mikko. 1992. Proofmarks. AFTE J 24 (1): 14-15.
2. Barnes, Frank. 1997. Cartridges of the World . Northbrook: DBI Books, Inc.
3. Bydal, B.A. 1990. Percussion primer mixes. AFTE J 22 (1): 1-26.
4. Dillon, J.H. 1991. The manufacture of conventional smokeless powder. AFTE J 23 (2): 682-688.
5. Dillon, J.H. 1991. Black powder background. AFTE J 23 (2): 689-693.
6. Gallup, A., and D.F. Schaffer. 1992. La Marine: The French Colonial Soldier in Canada 1745 1761 . Bowie: Heritage Books Inc.
7. George, W. 1988. Black powder firearms: Safety precautions. AFTE J 20 (1): 57-58.
8. Greener, W.W. 1910. The Gun and Its Development . New York: Cassel and Company.
9. Hackley, F.W., W.H. Woodin., and E.L. Scranton. 1967. History of Modern U.S. Military Small Arms Ammunition . New York: MacMillan.
10. Hatcher, J.S., F.J. Jury, and J. Weller. 1957. Firearms Investigation, Identification, and Evidence . Harrisburg: Stackpole Books.
11. Mathews, J.H. 1962. Firearms Identification, Volume I . Springfield: Charles C. Thomas.
12. National Rifle Association. 1961. Illustrated Reloading Handbook . National Rifle Association.
13. Smith, W.H.B. 1946. The NRA Book of Small Arms: Volume I - Pistols and Revolvers . Harrisburg: NRA/Military Service Publishing Company.
14. Smith, W.H.B. 1948. The NRA Book of Small Arms: Volume II - Rifles . Harrisburg: NRA/Military Service Publishing Company.
15. Smith, W.H.B., and J.E. Smith. 1973. Small Arms of the World, 10th Edition. Harrisburg: Stackpole Books.
16. Speer. 2007. Speer Reloading Manual #13 and #14 . ATK Ammunition Systems Group
17. Sporting Arms and Ammunition Manufacturers' Institute (SAAMI). Smokeless Powder. Wilton: Sporting Arms and Ammunition Manufacturers Institute
18. Styers, G.R. 1987. History of black powder. AFTE J 19 (4): 443-446.

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