The Complete Guide to Shotgun Ammunition Calibers: History, Usage, and Characteristics

By Derrick R. Stallings – HuntingOfficer.com

Shotguns are among the most versatile firearms in the world. Used by hunters, sports shooters, military forces, and home defenders alike, shotguns fire shells filled with multiple projectiles, called shot, or a single large projectile, known as a slug. One of the most defining aspects of any shotgun is its caliber or, more commonly, its gauge. Unlike rifles and handguns that use calibers measured in inches or millimeters, shotgun sizes are expressed in gauges, an archaic yet enduring system.

This blog dives deep into the various shotgun gauges, detailing their origins, characteristics, usage, and relevance in modern shooting.

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What is a Gauge?

The gauge of a shotgun is determined by the number of lead balls the same diameter as the shotgun’s bore that it takes to weigh one pound. For example, in a 12-gauge shotgun, 12 lead balls of the bore diameter would equal one pound. A 20-gauge shotgun requires 20 such balls. Thus, the smaller the number, the larger the bore diameter.

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12 Gauge: The King of Shotguns

History:

The 12-gauge shotgun emerged as the dominant gauge in the late 19th and early 20th centuries as firearms manufacturing became more standardized. It balanced power, versatility, and recoil, making it ideal for a wide variety of tasks.

Characteristics:

• Bore diameter: ~0.729 inches (18.5 mm)
• Shell lengths: 2 3/4″, 3″, 3 1/2″
• Common shot sizes: From #9 birdshot to 000 buckshot
• Versatile: Supports slugs, buckshot, and birdshot

Usage:

• Hunting: Deer, turkey, waterfowl, upland birds
• Sport shooting: Trap, skeet, sporting clays
• Home defense: Wide availability of defensive loads
• Military/law enforcement: Riot control, breaching

The 12-gauge remains the most popular shotgun size globally, offering the broadest selection of ammunition types.

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20 Gauge: The Gentle Alternative

History:

The 20-gauge gained popularity in the early 20th century, offering a lighter and lower-recoil option compared to the 12-gauge. It became a favorite among smaller-framed shooters and young hunters.

Characteristics:

• Bore diameter: ~0.615 inches (15.6 mm)
• Shell lengths: 2 3/4″, 3″
• Common shot sizes: Similar to 12-gauge, but with less payload

Usage:

• Hunting: Ideal for upland game, small deer with slugs, waterfowl with steel or bismuth shot
• Youth and beginners: Reduced recoil helps with comfort and accuracy

While less powerful than the 12-gauge, the 20-gauge can be just as deadly in capable hands.

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16 Gauge: The Forgotten Middle Child

History:

Once touted as the perfect compromise between 12 and 20 gauges, the 16-gauge was a favorite in the early 1900s. However, the lack of ammunition availability and standardized shotguns led to its decline.

Characteristics:

• Bore diameter: ~0.662 inches (16.8 mm)
• Shell lengths: 2 3/4″

Usage:

• Hunting: Upland birds, waterfowl, and medium-sized game

Despite a loyal following and recent resurgence among traditionalists, the 16-gauge remains a niche choice.

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28 Gauge: The Upland Specialist

History:

The 28-gauge was introduced in the early 1900s primarily for upland bird hunting. Its small size and minimal recoil make it a delight for long hunts.

Characteristics:

• Bore diameter: ~0.550 inches (14 mm)
• Shell lengths: 2 3/4″, 3″
• Lower shot payload, but very efficient in close ranges

Usage:

• Hunting: Dove, quail, woodcock, and other light game birds
• Sport shooting: Popular in skeet shooting

The 28-gauge is prized for its light weight and quick handling.

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.410 Bore: Not Technically a Gauge

History:

Often called the .410 gauge, this is a misnomer—it’s actually a caliber, measuring 0.410 inches in diameter. Introduced in the late 19th century, it was designed for small game and training purposes.

Characteristics:

• Bore diameter: 0.410 inches (10.4 mm)
• Shell lengths: 2 1/2″, 3″
• Very low recoil and small payloads

Usage:

• Hunting: Small game, snakes, and pests
• Beginner firearms: Common in youth-sized shotguns
• Specialized defensive loads: Especially in revolvers like the Taurus Judge

The .410 offers very limited power, but in skilled hands, it can be effective.

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10 Gauge: The Big Brother

History:

The 10-gauge was historically used for waterfowl and large game, especially before the rise of high-velocity 12-gauge loads. Once dominant in goose hunting, it has declined in popularity due to weight and recoil.

Characteristics:

• Bore diameter: ~0.775 inches (19.7 mm)
• Shell lengths: 3 1/2″
• High shot payloads and long range

Usage:

• Hunting: Large waterfowl like geese
• Specialized applications: Where maximum power is needed

Though powerful, the 10-gauge is often seen as overkill today due to advancements in 12-gauge loads.

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Other Historical Gauges (Rare/Obsolete)

8 Gauge:

• Mostly obsolete, once used for industrial shotguns and market hunting
• Illegal for migratory bird hunting in the U.S.

4 Gauge and 2 Gauge:

• Extremely large, black powder-era shotguns
• Rare and collectible, used for punt guns in waterfowl hunting

These gauges are more historical curiosities than practical tools today.

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Final Thoughts

Each shotgun gauge has its own unique place in history and usage. From the ubiquitous 12-gauge to the specialist 28-gauge and the niche .410 bore, shooters have a wide range of tools tailored to their needs. Understanding these gauges—not just their numbers but their history and characteristics—can help you choose the right shotgun for your application.

Whether you’re a seasoned hunter, a competitive shooter, or someone exploring shotguns for the first time, knowing your ammunition is a fundamental part of mastering the platform.

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