New hunters often tell me that cartridge nomenclature is the most confusing thing about firearms. Two questions usually top their list: what is a shotgun “gauge” and what is the difference between a “12 gauge” and a “20 gauge”?
If you’ve found yourself asking these questions, or wondering why larger calibers use smaller numbers, which caliber is best for waterfowl, or how shotguns are like pirate cannons, you’ve come to the right place.
What are shotgun gauges?
When we talk about a rifle or pistol “bore,” we are describing the inside diameter, or “bore,” of a gun barrel and the diameter of the projectile that can be fired through that bore. A 9mm Luger bullet is 9mm wide, for example, and can be fired through a 9mm bore. There are exceptions to this general rule, but that’s the gist.
Similarly, a shotgun “gauge” describes the width of the bore, but uses a different yardstick to do so. Technically speaking, the caliber of a shotgun is defined as “the weight of a solid ball of lead that fits perfectly in the bore of a shotgun expressed as the reciprocal of the weight of said ball in a fraction of a pound.”
That sounds more confusing than it is. For example, a lead ball that fits perfectly into the bore of a 12-gauge shotgun weighs 1/12the of a pound The lead sphere that fits perfectly in a 20-gauge shotgun weighs 1/20the of a pound, and so on. You can also think of this another way: how many lead balls the diameter of the shotgun bore does it take to equal one pound? The answer is the caliber of the shotgun.
This system of measurement hails from the days when a cannon could fire a lead ball weighing eight pounds, hence it was called an “eight pounder.” I could call his 12 gauge shotgun 1/12the pounder”, but you would have to wear an eye patch and have a parrot to do it.
Since larger lead balls weigh more than smaller lead balls, they take up a larger fraction of a pound. That’s why 12-gauge shotguns are larger in bore than 20-gauge shotguns, and 20-gauge shotguns are larger in bore than 28-gauge shotguns.
The most common exception to this rule is the .410 caliber. The inventor of the .410 was apparently tired of the caliber system, so he adopted the easier to understand caliber system. The diameter of a .410 shotgun is just 0.41 inches. For the curious, the lead ball that fits perfectly in a .410 caliber weighs about 1/67the of a pound, making the .410 a .67-gauge shotgun.
Shotgun Gauge Options
In theory, you could make a shotgun of any caliber, but manufacturers have settled on six options:
- 10 gauge (0.775 inches)
- 12 gauge (0.729 inches)
- 16 gauge (0.685 inches)
- 20 gauge (.615 inches)
- 28 gauge (.550 inches)
- .410 (.410 inches)
You can find shotguns in other gauges (24 and 32, for example), but these are much less common.
Most hunters know from experience that the 12-gauge and 20-gauge are the most popular, and that experience bears out at the gun counter. Midway USA, one of the largest online ammunition dealers, offers 487 12-gauge options and 157 20-gauge options. The next three spots are filled by .410, 28-gauge, and 16-gauge, respectively, but each has a third of the available options than 20 gauge.
The specific historical reasons for the popularity of these two indicators are beyond the scope of this article, but it’s easy to understand why they remain popular today. Both can be used for a wide range of applications, including hunting, target shooting, and home defense. Both are widely available from a variety of manufacturers, and both can be found in shotguns from every major gun company.
Either caliber can work effectively in almost any hunting scenario, but each has its own costs and benefits. Here’s how they break down in terms of ballistics, firepower, and versatility.
12GA vs. 20GA: ballistics
A 12-gauge shotgun has a power advantage over a 20-gauge, but unlike most cartridge comparisons, the faster projectiles are not the cause.
It is a common misperception that a 20 gauge is less powerful than a 12 gauge because it shoots pellets more slowly. Generally speaking, that is not the case. While a 12 gauge can be loaded at higher velocities on the top end, most 20 gauge shells push pellets about as fast as most 12 gauge shells. The difference is that a 12 gauge can accommodate more granules and sometimes larger on its shell.
A 12-gauge shell can be loaded with between 5/8 ounces and 2 ½ ounces of lead shot, with most loads flying between 1,200 and 1,500 feet per second. Federal, for example, offers a 2 ½ ounce TSS turkey load, a deer hunting shell loaded with ten #000 shot (the largest shot available), and a variety of Black Cloud waterfowl options with up to 1 ½ ounces. of payload. It’s safe to say that if you go for a 12 gauge, you’ll have more than enough power to get the job done in virtually any hunting scenario.
Twenty-gauge shells have a smaller diameter, so they can’t hold as many pellets as their 12-gauge cousin. The heaviest shot payload Federal offers is 1 5/8 ounces, the #2 buck is the largest buckshot available and Black Cloud payloads top out at 1 ounce. The pellets travel at similar speeds, but since there are fewer of them, the shot pattern is smaller and animals are harder to hit.
Of course, “difficult” is not “impossible”. A 20-gauge can do everything a 12-gauge can. You can hunt deer, waterfowl, upland birds, and turkey with a 20-gauge; you just have to have more practice to do it.
Overall, though, the 12’s larger capacity gives it a distinct advantage in this category.
12 GA vs. 20 GA: Shooting Capacity
The popularity of the 12 gauge can be explained by its ability to walk the line between powerful and painful to shoot. Larger gauge shotguns can throw more lead down, but for most people, those guns are too heavy and the recoil is too painful. Twelve-gauge shells have bruised many a shoulder, but with practice and a well-fitting shotgun, you can shoot all day without much discomfort.
But it’s hard to compete with the 20 caliber when it comes to shooting. Recoil is lighter on hunting shells thanks to smaller payloads, and 20-gauge shotguns can be designed to be lighter and more compact. Weatherby’s 12-gauge Element Waterfowler, for example, weighs 6.75 pounds, while the 20-gauge version of the same pistol weighs 6.25 pounds. You’ll save 0.8 pounds with the 20-gauge Orion-I and a full pound with the 18i Deluxe.
Shell cost is comparable, but a 20 gauge shotgun will generally be more “shootable” than a 12 gauge.
12 GA vs. 20 GA: Versatility
Versatility is the true strength of any shotgun. The ability to go after big game, small game, and birds with a single gun is why hunters keep coming back to their trusty smoothbore. No matter how many new high-velocity, low-drag rifle shells hit the market, there will always be a place for a shotgun in every safe.
But which of our two most popular shotgun calibers is plus versatile?
I’ll spoil the ending and tell you it’s the 12 gauge. The larger diameter of the 12 means it can shoot whitetail with larger slugs and buckshot for a more reliable kill. It offers a wider draft distribution for upland birds, better patterns for waterfowl, and heavier pellets for turkeys. The 20 gauge can target all of these species, but the 12 gauge can do better.
Why, then, does anyone choose to shoot a 20-gauge shotgun? In any scenario where weight and recoil matter more than power, the 20 caliber will be more “versatile” because the person behind the trigger will be more effective.
For upland hunters who take their shotguns long distances, a 20 gauge might be the way to go. Also, the short-range nature of most mountain bird shots mitigates the 12’s power advantage, and the 20’s lighter recoil never hurts anyone’s accuracy. Federal’s TSS loads have also bridged the gap in the turkey woods, making the 20 a great choice for the young or recoil-sensitive hunter.
Still, the ballistic advantage of the 12 allows it to target these species and more more effectively. It gets the thumbs up in this category too.
You may have noticed the frequent use of queer words like “usually”, “could” and “generally speaking” in this article. I do not recommend these qualifying words for powerful prose, but this subject requires them. The wonderful world of shotgun shooting is as varied and complicated as the animals we hunt, and the sheer variety of projectile options means almost any statement can be ruled out with a counterexample.
That’s inconvenient for me, but it’s great for you. It means you can find 12-gauge light pistols for long walks through highland territory. It means you can buy high-impact 20-gauge loads for waterfowl and 12-gauge loads that eliminate recoil for long days on the clay sports field. Regardless of what you want to do, you’ll be able to find an effective load in 12 or 20 gauge, which is the true beauty of shotguns.
But generally speaking, the larger 12 caliber offers more power and versatility, while the smaller 20 caliber offers better shot capacity. As the winner of two of the three categories, the overall winner must be the most popular sports frame of all time.