- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Shotshell Wads
Home > Small Arms Ammunition > Cartridge Case Manufacture > Shotshell > Shotshell Wads
Shotshell wads and one-piece plastic wads
Wads are used to prevent the mixing of propellants and pellets in a shotshell. The wad forms a critical gas seal at firing to keep the expanding gases behind the shot charge. Wads also act as spacers, setting the correct volume for the propellant and shot charges and cushioning the pellets to reduce deformation. For years, shotshell wads were simple disks of fiber, felt, or cardboard cut to fit the inside of a shotshell case. A hard, nonflammable wad, sometimes called a nitro wad, was placed over the powder.
In the 1960s, shotshell engineers realized that modern plastics could improve shotshell performance. Initially, plastic shot wrappers (simple flat sheets of polyethylene) were used to protect lead pellets from scuffing on the bore as they passed. Conventional fiber wads continued to be used after plastic shot wrappers appeared. Eventually, the hard-to-load plastic sheet material was replaced with an easily installed shot cup that was closed at the bottom.
The first plastic shotshells still used a metal rim assembly and a separate fiber base wad. The base wad provides support for the primer and controls powder space. Some fiber wads were plastic coated to prevent swelling. In some cases, the entire base wad was made of plastic and inserted in the tube.
Shotshell wads
It did not take long to realize that a contoured over-powder wad molded from plastic was more effective for obturation than the flat cardboard nitro wads. Molded with skirts to bear and seal against the barrel wall, these wads soon became commonplace, even when fiber wads were still used for spacing and cushioning. The evolution of wad design integrated the skirted base, pellet cushioning, and the pellet wrapper into one molded unit.
