Bullets are made of a lead alloy, often containing tin and antimony. Some bullets have a thick outer copper jacket for improved performance.

Cases are made of brass, steel, or aluminum, brass being the most common. Shotgun shells are often made with a polypropylene plastic case attached to a metal base. A few handgun cartridge cases have been made of plastic, but have not received wide acceptance. Primers are made of a copper or brass alloy cup with a brass anvil and are filled with an impact-sensitive lead styphnate igniter. The metal parts of the primer are usually nickel-plated to resist corrosion.

Propellants can vary from black gunpowder to a more modern smokeless powder which contains nitrocellulose. Propellants are carefully formulated to ignite and create an expanding gas that accelerates the bullet down the barrel. The expansion rate, physical size, shape of powder particles, and stability of propellant are all important factors in the chemical formula used to produce it.

Bullets can be made by several different processes. Smaller .22 caliber bullets are usually lead and are pressed, or cold formed, into shape. A small piece of thick lead wire is cut to a correct length and formed into the bullet shape by a dye set in an automatic press. High production rates can be achieved by this type of automated process. Many handgun and rifle bullets used for competition shooting are cast using conventional casting methods. The molten lead is poured into bullet mold cavity, cooled quickly, and then extracted from the mold. The point at which lead enters the cavity (or "sprue") is trimmed away as the bullet is extracted. Both cold-formed and cast bullets may be further improved by copper plating. The plating process electrically deposits a thin layer of copper on the outside of the bullet, protecting the lead from oxidation and providing a harder surface to engage the grooves, or rifling, in the barrel which give the bullet a spin to improve accuracy. Copper also reduces lead fouling of rifling after firing, allowing the firearm to maintain accuracy after firing many rounds.

To improve bullet performance and accuracy, the "jacketed" bullet was developed. This is a family of bullets that use a substantial brass or copper outer shell, usually filled with lead by casting or cold forming, and having several different configurations for specific performance criteria. Some examples are FMJ (Full Metal Jacket), JHP (Jacketed Hollow Point), and JSP (Jacketed Soft Point), each with options such as boattail design, controlled expansion, tracer, incendiary, and armor-piercing. The brass outer shell of these bullets engage rifling tightly upon firing, providing a close fit for improved accuracy. Designed to further improve accuracy, the boat-tail bullet has base reduced in diameter to improve air flow and stability in flight. The soft nose and hollow point bullets are designed to expand upon striking the target to intensify their impact.

Specialized bullets are sometimes found in military applications. Armor-piercing bullets can be solid brass or copper jacketed steel core. These can penetrate engine blocks and aircraft frames, damaging and incapacitating mechanisms inside. Tracers have a small amount of a phosphorus compound in their base. Upon firing, the phosphorous ignites and burns with a bright light. At night they can be seen streaking away from the firing position towards the target, allowing the shooter to track the bullet in flight and make aiming adjustments. Incendiary bullets contain small amounts of magnesium, which, like phosphorous, burns when ignited, but stays burning for a longer time and causes ignition of fuels or ammunition upon impact at the target.

Nearly all small arms ammunition cases are of brass alloy. Some use aluminum, steel, or plastic, but the brass case is most popular and easiest to manufacture.

The design of the case is determined by the firearm in which the ammunition is used. The typical brass case is formed from annealed sheet by drawing with a multiple punch and die set. The first stage of the multiple die set forms the metal, the second stretches the metal deeper, the third forms the rim, and so on. Each step stretches the metal slightly farther until the final stage produces an accurately formed case. The cases are trimmed to length and the primer hole is punched. Heat treating and stress relieving are performed to selected types of cases to improve durability. This is accomplished in large batch ovens, where baskets of cases are heated with enough temperature to gently soften the metal without distorting it. When cooled, the metal is "relaxed" and better able to take the punishment of firing. Some handgun caliber cases are nickel plated for durability in reloading, corrosion resistance, and for appearance. Each case is stamped with information such as caliber, manufacturer, munitions codes, and year of manufacture.

The primer consists of two metal parts and a small amount of explosive compound. Primers come in different sizes depending on the firearm. Using a small pistol primer as an example, the cup is usually about 0.125 inch (0.32 cm) in diameter and 0.125 inch (0.32 cm) tall, and made of soft copper or brass. Inside is placed a small amount of the impact-sensitive explosive lead styphnate, and pressed into the opening is a triangle shaped piece called the anvil. When struck by the firing pin, the center of the cup collapses, squeezing the explosive between its inner surface and the anvil. The explosive ignites and shoots a flame through the flash hole, igniting the propellant to fire the cartridge.

The assembly process for the cartridge components begins with a thorough cleaning and polishing of the case by a vibratory finisher. The finisher works by vibrating a corn byproduct (dried and ground corncobs) with a polishing compound around the cases, creating a high luster. Thus prepared, they are ready for final assembly. This is how a typical center-fire metal cartridge is assembled:

• Sizing the case: The cases are fed into a loading press which first sizes the case. This sizing forms the metal case to standard dimensions. The case must be within 0.001 inch for it to function correctly.
• Inserting the primer: The primer is then pressed into the case primer hole flush with the base. The primer must be flush or the cartridge will not feed properly in the weapon magazine, causing a "jam." At the same time, the mouth of the case is slightly expanded, in preparation for receiving the bullet.
• Charging the case: The case is "charged," or filled with the correct amount of propellant. This step is of utmost importance, for miscalculation or double charging could be disastrous.
• Assembling the bullet: The bullet is firmly seated into the open end of the case. The bullet has a coating of lubricant to prevent corrosion and assist in the assembly process. The bullet is then crimped into the case to give the correct overall length of the cartridge. The crimp reduces the diameter of the open end of the case and captures the bullet tightly, sealing the assembly together so moisture cannot invade the powder. The press used to assemble cartridges must feed each component accurately and in the correct sequence. Otherwise, cases could be unprimed, powder left out, or bullets seated incorrectly. Any of these could result in a misfire or loss of accuracy at the minimum and, at worst, cause the firearm to blow apart upon firing. In each stage of the process, special dies perform the important assembly function. The dies are made of tooling carbide for long life, and have close adjustments to produce quality ammunition. After assembly, the finished cartridges are packaged, usually 50 to a box, and prepared for shipment to the shooter.

Most manufacturers shoot thousands of their own cartridges as part of their quality control programs and processes. The accuracy, pressure, reliability, velocity, and consistency are all recorded. The weapons used for this are specially made, highly accurate, and equipped with data-gathering electronics. Each production run of a particular cartridge is given a "lot code." This number, printed on the ammunition box, allows ammunition to be inventoried and traced. Should a particular lot show problems in the field, that group can be recalled and replaced using the lot code system.

Small arms ammunition will be available in its present form for the foreseeable future. Its function will continue to be to propel a projectile over a distance to strike a target. Variations in the material and design of this ammunition will be in response to the specific needs of the many groups of small arms users.

The military will continue to develop ammunition which can penetrate and incapacitate a wide variety of targets ranging from humans to sophisticated electronic equipment. Currently, they are investigating "non-lethal" weapons and ammunition which will incapacitate a target without destroying it. Small arms weapons in this category include hand-held chemical lasers to knock out electronic sensors, and foam guns which shoot a sticky foam that envelops the target. These non-lethal devices would supplement, not replace, the conventional small arms weapons and ammunition.

Police are also interested in non-lethal weapons and ammunition. Rubber bullets that impact without penetration are already in use for riot control. Another device is a shotgun which fires a small bean bag. When fired at a close range, the bean bag hits with the impact of a punch to momentarily incapacitate the target.

Hunters will want ammunition which hits accurately and kills with a single shot. Much of the development of commercial small arms ammunition has been in this area, and has included many variations in powder loads and bullet configuration.

Target shooters will continue to develop ammunition which offers excellent accuracy and repeatability for competition shooting.