Module 5: Small Arms Ammunition
Components of Ammunition
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Historical Development of Propellants
Projectile Manufacture Methods
Cartridge Case Manufacture
Primer Manufacture Process
Ballistic Testing
Reloading Process
Projectile
Cartridge Case
Primer
Propellant
Small arms propellants all share a common origin in nitrocellulose, which is made by treating cellulose with nitric acid in the presence of sulfuric acid
most cellulose came from cotton linters until it was replaced with wood fibers as synthetic fibers began replacing cotton
Different sizes and shapes of granules (the individual particles of propellant powder) are used for different purposes/needs
Disk/Flake Propellants - used in low-pressure, low-volume applications (like handguns and shotshell ammunition); produced by die extrusion
Cut sheet/Lamelle - used in modern propellants for smaller/low-pressure cartridges; burning characteristics are identical to extruded disks
Cylindrical Propellants - medium- to slow-energy release
Ball Powders/Flattened Ball Powders - nitrocellulose that is suspended in solution to achieve varying diameters that are used for small arms
After forming and drying the granules, they are tested with a calorimeter bomb to ensure they meet standard specifications
Casting - molten lead is poured into a mold
Swaging - requires a punch and a die that is shaped to match the desired profile
Drop Shot - drop shot (small lead pellets) were produced in a structure called a shot tower
Lead Free - molten steel and other alloys are ejected at a high speed and pressure into a water spray booth where they form sphere pellets; pellets are then separated by size
Jacketed - an outer skin or jacket was added to lead bullets when smokeless propellants replaced black powder due to the higher pressures and temperatures
lead was melted in a large vat at the top of the shot tower
the lead flowed down into a broad, shallow pan with fine holes in the bottom that was being struck several times per second
the molten lead flowed as streams from holes in the stationary pan, while vibrations from the impact broke the streams into randomly sized droplets
the droplets become rounded due to gravity and surface tension
the rounded pellets fell into a tank of water for collection and cooling
pellets were finally separated by shape and rejected pellets were recycled
Metallic
depriming (removing the old primer using a decapping die)
cleaning the cases with hot water and soap or a commercial cleaner
polishing
inspecting cases to ensure physical integrity
lubricating the case
resizing the case
trimming the case to an appropriate length
priming the cases
charging the case
seating the bullet with a bullet seating die
crimping the cartridge case mouth into a bullet cannelure
Dies and tools used in reloading can leave unique, identifiable toolmarks and impressions that crime scene investigators can use
cartridges are tested against both company standards and those recommended by the Sporting Arms and Ammunition Manufacturers Institute Inc.
pressure testing
velocity testing
function firing
accuracy testing
customized specifications
cosmetic evaluation
testing is based on accepted statistical sampling procedures
testing destroys the cartridges
a wet mix of the priming compound (which includes lead styphnate, antimony sulfide, barium nitrate, and other chemicals that will create heat and gas when struck sharply) are forced into small holes to create a fixed volume
the filled plate is placed over a tray of rimfire cases that has the same hole pattern as the charge plate
a third plate is pressed through the charge plate; this plate has multiple pins that correspond to the hole pattern in the charge plate
the disks of priming mix fall into the cases
Shotshell
used in rifles and handguns
made completely of metal, with the raw material being brass (copper and zinc at 70:30)
made of hybrid materials, using metals with paper or plastic