Gauge in a gun is a traditional unit of measurement primarily used for the bore diameter of shotguns. It defines the internal diameter of the barrel, which in turn determines the size of the shotshells it can fire.
Understanding the Gauge Measurement System
Unlike rifles and handguns that use caliber (a direct measurement of the bore in inches or millimeters), shotgun gauge is determined by a unique historical method.
The gauge number represents the number of pure lead spheres that, when each has a diameter equal to the approximate internal bore of the shotgun, collectively weigh exactly one pound (approximately 453.59 grams).
- Example: A 12-gauge shotgun has a bore diameter such that it would take 12 pure lead balls of that exact diameter to weigh one pound.
- Inverse Relationship: This means that a smaller gauge number indicates a larger bore diameter. For instance, a 10-gauge shotgun has a larger bore than a 20-gauge shotgun.
This system originated in the British Empire and is still widely used today for shotguns.
Common Shotgun Gauges and Their Uses
Different gauges offer varying capacities for shot payload and different recoil levels, making them suitable for specific applications.
Popular Gauges Explained:
- 12-Gauge: This is by far the most popular and versatile shotgun gauge. It offers a balance of power, range, and shot capacity, making it suitable for:
- Hunting (waterfowl, upland birds, deer with slugs)
- Sporting clays, trap, and skeet
- Home defense
- 20-Gauge: Often referred to as the "smaller sister" of the 12-gauge, the 20-gauge offers lighter recoil and is an excellent choice for:
- Youth and smaller-framed shooters
- Upland bird hunting (pheasant, quail, grouse)
- Small game hunting
- Home defense (with appropriate loads)
- 10-Gauge: This is one of the largest gauges commercially available. Its large bore allows for very heavy shot payloads, making it ideal for:
- Long-range waterfowl hunting (geese, ducks)
- 28-Gauge: Known for its light recoil and elegant handling, the 28-gauge is favored by many for:
- Upland bird hunting
- Skeet shooting
- .410 Bore: While commonly referred to as a gauge, the .410 is technically a caliber, measuring 0.410 inches in diameter. It does not follow the lead ball weight definition. The .410 is known for:
- Very low recoil
- Beginner training
- Small game and pest control at close range
Shotgun Gauge Chart
The table below illustrates common shotgun gauges and their approximate bore diameters:
| Gauge / Bore | Approximate Bore Diameter (inches) | Approximate Bore Diameter (mm) | Primary Applications |
|---|---|---|---|
| 10 Gauge | 0.775 | 19.69 | Waterfowl hunting |
| 12 Gauge | 0.729 | 18.52 | All-around hunting, sport shooting, home defense |
| 16 Gauge | 0.665 | 16.89 | Upland bird hunting (less common today) |
| 20 Gauge | 0.615 | 15.62 | Small game, upland birds, youth, low-recoil applications |
| 28 Gauge | 0.550 | 13.97 | Upland birds, skeet, light recoil |
| .410 Bore | 0.410 (Caliber) | 10.41 | Small game, pest control, training, very low recoil |
Gauge vs. Caliber
It's important to differentiate between gauge and caliber:
- Gauge: Used for shotguns, referring to the number of lead balls of bore diameter that weigh one pound.
- Caliber: Used for rifles and handguns, referring to the exact diameter of the bore and bullet, typically measured in fractions of an inch (e.g., .22, .308, .45) or millimeters (e.g., 9mm, 7.62mm).
Understanding gauge is essential for selecting the correct ammunition for your shotgun and for choosing the right firearm for a specific purpose. For more information on firearms and their specifications, reputable sources like NRA or Wikipedia can provide further details.
