base of a bullet—can have major impacts on the cost of production and, perhaps, the feasibility of compliance with proposed changes.
We have already touched on some aspects of manufacturing in describing the anatomy of firearms and ammunition earlier in this chapter, and aspects of manufacture will arise in Chapter 3 as well (particularly in discussing challenging issues for firearms identification, generally). This section introduces basic issues but is not a comprehensive discussion.
The manufacturing of most guns is highly automated and generally efficient, and as many as 5 million new firearms (domestic and foreign) enter the U.S. market each year. Befitting its historical development, dating to Samuel Colt’s popularization of interchangeable parts and production line assemblies, the modern firearms industry remains one that is characterized by solid process control. That is, the process of mass-producing firearms is one that can be well partitioned: constituent parts of a new firearm can be drawn from large bins of fairly standardized parts and automatically fitted together with low yield loss, resulting in weapons of reasonably identical properties in terms of size, weight, and performance.
Yet individual manufacturers differ on the exact steps used in machining and assembling firearms, and choices on the amount of filing or polishing to do on firing pins or whether to apply paint to the breech face can have an impact on the resulting toolmarks. In addition, some manufacturing techniques affect the type and quality of marks created in firing. Champod et al. (2003:307) argue that “machining marks made by grinding, filing and some other machining methods are random and hence we expect no repeatability between tools.” In comparison, “machining marks made by stamping, some cutting processes such as broaching, and some forging processes may be repeatable.”
Various manufacturing techniques used by Lorcin Engineering drew interest in the 1990s, as firearms produced by the firm became more widely used in crimes;5 they serve as useful illustrative examples. Thompson (1996:95) found two Lorcin L9MM semiautomatic pistols, bought at the same time, that produced sufficiently similar breech face markings that a match could be made to either weapon on that mark alone; they could, however, be distinguished by sidewall and extractor marks. Similarly, Matty
In 2000, the Lorcin L380 semiautomatic pistol was the most traced firearm after recovery from juvenile possessors, and a Lorcin .25 caliber pistol ranked seventh. The L380 was also traced with high frequency after recovery from older offenders, ranked second among firearms recovered from 18–24-year-olds, and ranked third among firearms recovered from adults aged 25 and older (U.S. Bureau of Alcohol, Tobacco, and Firearms, 2002:15–16).