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Small Arms Ammunition
retrieved Feb 5, 2020, https://firearms-examiner…
Small Arms Ammunition
retrieved Feb 5, 2020, https://firearms-examiner.training.nij.gov/
Module 5
Objectives
- describe the components of ammunition
- describe the historical development of propellants, both single and double based
- define bullet jacket types and materials
- describe projectile manufacture methods, jacket manufacture technologies, steps in cartridge case manufacture, shotshell manufacture process, primer manufacture process
- differentiate between the primer manufacture process for rimfire and centerfire cartridges, between shotshell and cartridge primer manufacture
- describe the steps in the ammunition assembly process, steps in ballistic testing, steps in the shotshell assembly process, the reloading process and how it can be used for firearm identification.
Components
- Making any ammunition product requires that subassemblies
- Projectile
- Propellant
- Primer
- Cartridge Case
Propellants
- Modern small arms propellants all share a common origin, nitrocellulose
Morphology
- granules
- Disk or flake propellants
- Cut sheet or lamelle
- Cylindrical propellants
- Ball powders and flattened ball powders
Die Extrusion
- Processing the plasticized nitrocellulose mass combines extrusion with rotating cutters to produce the desired shape
Drying
- newly cut propellant granules contain residual moisture
- dried to reduce the moisture content to the level required in the finished product
Deterrent Coatings and Stabilizers
- Deterrent coatings can help to slow the rate of energy release
- Stabilizers are preservatives used to increase storage life
Testing, Grading, and Blending
- Each new batch of propellant is tested for performance against a retained reference lot of that propellant.
Canister and Bulk
- canister propellant is sold in small quantities to hobbyists who reload ammunition
- Bulk propellants are sold to manufacturers that possess standard pressure-testing equipment making reliance on published data unnecessary.
Projectiles
Casting
- oldest manufacturing method
- advantages, such as the ability to produce sharp edges and detailed surface features
Swaging
- requires a punch and die set mounted in a press, providing a mechanical advantage
Shot Pellets
- formed by the action of gravity on molten lead.
- usually hardened with traces of antimony or arsenic to reduce deformation
-
Lead-Free Shot Pellets
- Concern over the potential effects of the ingestion of lead shot by waterfowl led to the adoption of lead-free shot for hunting
Lead-Free Bullets
- All-Copper Bullets
- Hybrid Bullets
- Frangible Bullets
Jacketed Bullets
- Bullets with metal jackets
- Since pure copper is difficult to cold-work, copper alloys became the standard jacket material
Cup and Draw Operation
- Jackets are produced in cup and draw operations
- Dies and punches in the press blank out a disk of the sheet metal and simultaneously form it into a shallow cup.
- basic requirements for cups are concentric wall thickness and relatively even tops.
- jacket is trimmed to meet specifications
Other Jacket-Forming Technology
Full Metal Jacket
- requirement: the base is closed after the core is tamped
Bullet Features
- fluted or segmented edges can not be produced during final forming.
- Jacket flutes can be added in the last draw operation
Assembly
- Feeding the components into a machine capable of applying pressure
- Providing forming dies in the machine
- Providing a way to move parts from one station to the next
Machinery
- most pervasive press for bullet assembly is the transfer press
- Bullet assembly can also be performed on a dial or rotary press
Open Point
- shaping the point
- point shaping is performed in multiple steps to avoid excessive load on the bullet and/or the equipment
Finishing
- bullets are usable but some may require processing to add other features
- the bullets are covered in processing oils and need to be cleaned
- Bullets need to be tested
Cartridge Case Manufacture
Metallic
Head-Turning Operations
- finishes the exterior shape of the case head
- performed in a small automated lathe
Taper, Trim, and Neckdown
- Most cases are ultimately tapered to some degree
- small taper = one die
- more pronounced tapers = taper is produced progressively to reduce stresses
- case is trimmed to the specified length
Stress Relief, Annealing, and Hardness
- ammunition is loaded and stored without addressing the stresses, cracks can appear in the bottleneck area
Inspection
- physical dimensions are checked against engineering specifications
- cases may be set aside for grain structure evaluation and/or micro-hardness testing
Rimfire
- start as rolled, thin sheets of cartridge brass, which are mounted and fed through rollers to re-flatten them
Centerfire
- centerfire cases start as cups
- the raw sheet brass required for these cases is often thicker than that used for rimfire cases
Drawing Operations
- leaves enough material in the base to form the web of the case
- web provides support for the primer and reduces the amount of swelling that can occur during firing
- Heading also forms the rim
Alternate Materials
- Brass
- Mild Steel
- Aluminum alloy
Shotshell Wads
- Wads are used to prevent the mixing of propellants and pellets in a shotshell
- act as spacers
Primer Manufacture
- smallest component in ammunition
- class of ammunition determines how priming is accomplished
Testing
- After spinning, the cases are placed in low-temperature ovens to eliminate the moisture
- cases are tested for primer sensitivity.
Centerfire
- more complex because of their internal components
- all have primer cup, anvil, primer chemicals or mix.
Shotshell
- have additional part called battery cup
- shotshell anvil is larger
Ballistic Testing
Testing is destructive; tested cartridges are expended
cartridges undergo testing in the following areas:
- pressure
- velocity
- function
- accuracy
- customized specifications
- cosmetic evaluation
Pressure
- ensure that the pressure generated at firing does not exceed the standards
Velocity and Function Firing
- velocity is also a parameter that must fall within a range of values in order to ensure uniform performance and to reflect the advertised specifications for the load
- A portion of the statistical sample must be fired in production firearms
Accuracy and Custom Specifications
- accuracy testing is performed in fixed mount barrels to reduce the human factors that can contribute to poor accuracy
- Testing against customized specifications is performed when a particular lot of ammunition is assembled for a customer with specific needs