Understanding the Sizes and Names of Ammunition: .22, 9mm, and More

When navigating the world of firearms and ammunition, one of the first challenges is understanding the myriad of names and sizes assigned to different types of ammunition. Common examples like .22 and 9mm may seem straightforward, but others like .222, .223, 5.56, 220 Swift, and 22-250 can be confusing without a clear understanding of how these designations are defined. In this article, we'll explore the logic behind these names, the differences between them, and provide tips for making sense of the various ammunition types.

Deciphering the Names and Sizes

Ammunition names are often a reflection of either the bullet diameter or the rifle barrel diameter, regardless of the specific calibre designation. For instance, a .22 caliber bullet refers to a bullet that measures 0.22 inches in diameter. When you see a name with a '.22' prefixed with other descriptive names like 'rimfire', 'short', 'long', 'long rifle', or 'magnum', these descriptors indicate variations in the cartridge design.

Understanding the Diameter

Most modern ammunition is described by the diameter of the bullet or the bore of the firearm. For example:

The '.22' in '.22 caliber' refers to a bullet that is 0.22 inches in diameter. The '9mm' refers to a bullet that is 9 millimeters (mm) in diameter. The '5.56mm' refers to a bullet that is 5.56 millimeters in diameter.

When you encounter names with numbers and letters (like .222, .223, 5.56, 220 Swift, and 22-250), it's essential to understand the context in which they are used. These names often refer to the specific attributes and performance of the ammunition, such as its loading, intended use, or relative power.

Shotgun Ammunition

In shotgun ammunition, the diameter is referred to using a more complex system:

'12 gauge' '20 gauge' '410 bore'

The 12 and 20 gauges are derived from the diameter of the bore, measured in hundredths of an inch. The .410 is the smallest and is equivalent to a 7/8-inch bore. Understanding these measurements is crucial when purchasing or shooting shotguns.

Ammunition Types

Ammunition is categorized by its purpose and design. To make sense of the various types, consider the following guidelines:

Point before numbers (e.g., .22): These refer to inch-defined calibers within the inch-based system. Gauge behind numbers (e.g., 12 gauge): These refer to shotgun ammunition. Otherwise (e.g., 9mm, 5.56mm): These refer to metric system-defined calibers.

While these guidelines provide a starting point, some exceptions to the rule do exist. For instance, .357 caliber ammunition is actually derived from a .38 caliber pistol, which sometimes leads to confusion.

Practical Tips for Making Sense of Ammunition

The most practical way to understand and work with ammunition is through hands-on experience. Here are some tips to help you make sense of the different types of ammunition:

Learn the Guidelines: Familiarize yourself with the common calibers and their designations. For example, a .30 caliber refers to a bullet that is 0.30 inches in diameter. Study the Patterns: Develop an understanding of the patterns and variations, such as the .357 being a .38 caliber pistol. Consult Reliable Resources: Reference reputable sources like manuals, firearm manufacturers, and shooting clubs to learn about the different types of ammunition. Practice with Calibrated Equipment: Use equipment like calipers to measure bullet diameters and ensure accuracy.

Understanding the sizes and names of ammunition is critical for safe and effective use. If you cannot accurately discern the calibre by sight, there is no reason to handle or shoot any firearm. Even a trained chimp could pick the correct bullet from a selection and fire it, so make sure you are well-informed and prepared.

Conclusion

With a solid understanding of the various calibers, their designations, and practical tips, you can navigate the complex world of ammunition with confidence. Whether you are a seasoned shooter or a beginner, taking the time to understand the different types of ammunition is essential for safe and effective use. Always prioritize your safety and the safety of others by staying informed and prepared.