Bullet swaging is a cold manufacturing process for bullets that relies on extreme pressure to form the metal. Rather than melting metal and pouring it into molds, the manufacturer presses room temperature materials into a die. Punches can exert tremendous pressure to force the metal to conform to the shape of the die, creating a finished bullet. This technique can yield bullets of better quality and more accuracy, although it can also be more expensive.
Some companies produce swaged bullets for commercial sale. The packaging usually indicates that this production technique has been used, and should provide information about the size and composition of the bullets. It’s also possible to accomplish this with a home workbench and some basic metalworking equipment. Tools for bullet swaging are available from a number of sources. A metalworking shop may also have equipment suitable for this purpose and could be willing to rent bench space.
Casting, a traditional production method, has a number of flaws. The first is that the size of the bullet may be less precise, because the metal is heated and it changes size when it cools. Companies have to manufacture very precise molds to provide enough room for cooling without making the bullets too large. In addition, small cracks and bubbles can develop during casting, which may lead to problems when a bullet is fired. Neither of these issues develop with bullet swaging, which can yield bullets with better performance.
Quality control in the use of bullet swaging for production of ammunition can include measurements to make sure bullets are of uniform size and shape, along with assays to check on the metal composition. People making their own can use a variety of dies and punches to get specific shapes, including hollowpoints and other bullets with extra features. Making bullets can allow people to precisely control their composition and shape for specific purposes and increased quality control. It is not necessarily cost effective, as the investment in equipment and supplies can be high.
The best option for people buying and making bullets can depend on how they use them. Some people prefer the increased accuracy available with bullet swaging. Others may not notice a significant difference, or might be willing to accept a tradeoff with cast bullets. It may be possible to get bulk discounts on large orders of bullets or raw materials, something to consider for those with concerns about expense.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.