As you can imagine, we often receive questions about firearm calibers and gauges. Usually, guests want to know the best caliber for a specific use such as self-defense or practicing on the range. And truthfully, it’s not always an easy, clear-cut answer. There are many rifle and handgun calibers available to the public along with a mind-boggling array of ammunition. The shooting sports community has long debated which is the “best” for various activities. Firearm magazines and shooting blogs thrive from the ongoing debate. However, if you’re new to firearms, understanding the basics of calibers and gauges can be challenging. To help you make sense of common shooting terms, we’ve compiled a few tips. Keep in mind that we tried to make these descriptions as simple as possible. We will share more in-depth explanations and details in future posts.
The word “bore” can mean many things. In the shooting sports world, bore refers to the inside of a firearm’s barrel. The majority of traditional shotguns utilize what is known as a smooth bore. The inside of a smooth-bore barrel has an even, or smooth surface. Rifles and handguns feature rifled barrels that have a grooved pattern machined into the barrel’s inner surface. If you look inside a rifled barrel, you can actually see this “twist.” Rifling creates torque and causes a bullet to spin, giving it improved stability and increased accuracy over a smooth-bore firearm.
The term “caliber” refers to the diameter of a rifle or handgun’s bore. It can also refer to the diameter of a bullet. Firearm calibers are usually measured in millimeters, hundredths of an inch or thousandths of an inch. For example, a 9 mm handgun has a bore that measures approximately 9 mm in diameter. A .223 rifle has a bore that measures approximately 223/1000 of an inch in diameter.
Note: It’s important to say approximately here because there can be minute differences in bullet and barrel size depending on the caliber, brand, etc.
This is where calibers can start to get confusing. Unfortunately, there isn’t an industry-wide standard for denoting bore/bullet size. A great example is the ever-popular .30-06 caliber. The -06 has nothing to do with barrel or bullet diameter. Instead, it comes from the year 1906 when the caliber was introduced to the US Army. The .30-06, .30-30, .308 and .300 Winchester are all 30-caliber, but each bullet is a different size. When it comes to caliber sizing, it seems like there’s an exception for many of the rules.
When you hear the term “gauge” in shooting sports, it’s usually referencing a shotgun. Similar to caliber, gauge denotes the inside diameter of a shotgun barrel. It’s a much older form of measurement that relies not on the actual dimension of the barrel, but on the weight of lead that will fit inside the barrel. While it sounds complicated, just remember that the smaller the gauge, the larger the size of the firearm’s bore. For example, a 12-gauge shotgun has a larger bore than a 20-gauge shotgun.
Note: One exception to the gauge rule is the .410 shotgun, which is actually measured by caliber not gauge.
Cartridge Versus Bullet
The terms bullet and cartridge are often used interchangeably by many shooters. Hang around a gun store or shooting range for long and you’ll hear this from visitors. However, cartridges and bullets are not the same thing. A firearm cartridge is the entire assembly. A cartridge contains a case, primer, propellant and a projectile. The bullet is the actual projectile that’s fired from the firearm. It’s only one component of a cartridge.
Note: Shotguns use shot or slugs.
Regardless of what caliber or gauge you plan to use, take the time to make sure you have the proper ammunition before loading your firearm. All modern firearms are stamped with the correct caliber or gauge on the barrel. Always double-check your firearm and ammunition to ensure they match.
Ask Our Experts
When it comes to shooting firearms, there are no dumb questions. If you’re unsure or in doubt, it’s always best to ask an experienced professional for insight. Triangle Shooting Academy has a team of seasoned firearms experts who will be happy to answer your questions. Stop by our facility or give us a call today at 919.802.2040.