By Anthony Mitchell
Introduction
In this article we will take a look at the shotgun cartridge, how it works, and some of the terminology surrounding it. This article concentrates on the 12 gauge, as this is the most commonly encountered.
The shotgun cartridge is of the centrefire type. The ones commonly encountered have a plastic case; previously, cases were made of cardboard.
The cartridge contains a powder charge and a wad, topped off with a load of shot. The case is then crimped over.
The “standard” 12 gauge load was usually a 3 dram equivalent, 2¾ inch cartridge with a payload of 1⅛ ounces of shot. This gave a muzzle velocity of approx. 1200 feet per second.
Calibre
Shotguns and their cartridges are usually described by the term “gauge”, and relate to the diameter of a lead ball. A 12 gauge gun barrel has the diameter of a lead ball, 12 of which would weigh one pond. A 20 gauge gun barrel has a diameter of a lead ball, 20 of which would weigh one pound. In the UK, they use “bore” instead of gauge. E.g. 12 bore instead of 12 gauge.
As always, there is an exception to the rule. The .410 shotgun has a bore diameter of .410 of an inch.
Dram Equivalent
A dram is a unit of measurement in the Imperial system. A common load was 1⅛ ounces of shot propelled by 3 drams of black powder. When smokeless powder came into being, shooters wanted to know how powerful a particular load was. Thus the term “dram equivalent” came into common usage.
Case Length
The case length is specified after the cartridge has been fired. A standard shell is 2¾ inches or 70 mm long. Some guns are chambered for 3 inch shells. Do not use 3 inch shells in a gun chambered for 2¾ inch shells. To do so may give rise to dangerous chamber pressures and risk of injury to the shooter.
Shot
The standard load was previously 1⅛ ounces (32 grams). Loads used for clay target shooting are usually 1 ounce (28 grams). Field loads are often heavier than this.
Shot Size
In the smaller shot sizes, pellets are given a number according to their size. The larger the number, the smaller the pellet size. E.g. No. 4 shot is bigger than No. 7. Larger shot sizes are given a letter descriptor. (For instance, SG has 9 pellets in a 32 gram load).
The shells in Fig. 1 are Remington 12 gauge with 28 grams of 7½ shot
Wad
The wad sits between the powder charge and the shot, and is usually cup-shaped and made of plastic. Sometimes they are made of cork or similar material. The wad protects the shot as it travels down the barrel.
Steel Shot
Due to environmental considerations, some field loads contain steel shot instead of lead. As steel is much harder than lead, it should only be used in guns designed for steel shot.
Points to Remember
- Always check that the shells are compatible with the gun.
- Ammunition manufacturers put a lot of useful information on the box, take the time to read it.
Until next time, have a happy and safe shoot!