The term "caliber" refers to the diameter of a projectile, usually expressed in inches or millimeters. However, the term isn't directly applicable in the same way to a 12-gauge slug as it is to other firearm cartridges. This is because "12 gauge" isn't a caliber measurement in the traditional sense.
Understanding Gauge vs. Caliber
Gauge, used for shotguns, refers to the number of lead balls of a given diameter that would weigh one pound. A 12-gauge shotgun means that 12 lead balls of that bore diameter would weigh one pound. The larger the gauge number, the smaller the bore diameter.
Caliber, on the other hand, directly measures the diameter of the projectile. For example, a .30-caliber bullet has a diameter of 0.30 inches (7.62mm).
The Diameter of a 12 Gauge Slug
While not expressed as a caliber, a 12-gauge slug does have a measurable diameter. This diameter varies slightly depending on the manufacturer and the specific slug design, but generally falls within the range of approximately 0.73 inches (18.5mm). It's important to note that this is the bore diameter, not necessarily the exact diameter of the slug itself, which may be slightly larger or smaller depending on the design.
Why the Confusion?
The difference between gauge and caliber often leads to confusion. While a 12-gauge shotgun fires a projectile that's approximately 0.73 inches in diameter, we don't typically refer to it as a ".73 caliber" slug. The established terminology of "12-gauge" is deeply ingrained in the shotgunning community and industry.
Different Types of 12 Gauge Slugs
It's also important to understand that the diameter of a 12-gauge slug can vary slightly depending on the type of slug. Different manufacturers may use varying designs that result in minor dimensional differences. Common types include:
- Rifled slugs: These slugs have grooves that impart spin for increased accuracy.
- Foster slugs: A common design that's relatively inexpensive and widely available.
- Brenneke slugs: Known for their longer range and penetration capability.
In summary, while you won't find a "caliber" designation for a 12-gauge slug in the same way as with rifle cartridges, the approximate diameter of the projectile fired from a 12-gauge shotgun is around 0.73 inches (18.5mm). Remember that this is an approximation, and slight variations can occur.
