12-gauge cartridges come in a multitude of different lengths. The most common are: 2.75-inch, 3-inch, and 3.5-inch, each with varying loads and similar ballistics. The 12-gauge cartridges also come in several loads, both birdshot and buckshot, as well as slugs.
Typical 00 buckshot comes with nine pellets of buckshot in the cartridge, and each pellet is roughly .33 caliber in diameter. Birdshot is numbered similarly to buckshot; however, the pellets for birdshot are typically much smaller and more numerous, as they are intended for shooting birds, and not larger animals (or people).
Shotgun shells of the same caliber are classified by the size of the shot contained within the cartridge. The smaller the number preceding the type of shot used in the cartridge, the larger the diameter of the individual pellets. Listed from largest to smallest:
- 0000 Buckshot - .38 caliber, 8 pellets of buckshot
- 000 Buckshot - .36 caliber, 6 pellets of buckshot
- 00 Buckshot - .33 caliber, 8-9 pellets of buckshot
- 0 Buckshot - .32 caliber, 9 pellets of buckshot
- #1 Buckshot - .30 caliber, 10-11 pellets of buckshot
- #2 Buckshot - .27 caliber, 15 pellets of buckshot
- #3 Buckshot - .25 caliber, 18 pellets of buckshot
- #4 Buckshot - .24 caliber, 21 pellets of buckshot
The larger the individual pellets, the smaller the number (down to 0000, pronounced "quadruple-ought").