Even if you haven’t had any experience with a shotgun, you’ve probably heard the term “gauge”, as it related to a shotgun, before in movies, TV shows or the news. The gauge refers to the bore size of the barrel, or in other words, the inside diameter of the barrel. Except the gauge number doesn’t actually refer to the size of the bore itself, but the weight , in fractions of a pound, of a solid sphere of lead with the diameter of the sphere equal to the inside measurement of the barrel. So a 12 gauge has the barrel diameter that would fit a lead ball that weighs 1/12th of a pound (.729 inches in diameter)
It is confusing when you first hear it and it’s the not in any way relatable to how rifles and pistols are measured, but there it is nonetheless. The main fact to keep in mind is that the smaller the number of the gauge, the larger the bore of the weapon. So a 20 gauge shotgun is much smaller than a 12 gauge. Luckily, there are much less gauges of shotguns than there are calibers of rifles and pistols, and there are really only 2 or 3 gauges that are common with the most popular being a 12 gauge.
We’ve adopted this gauge measurement from the way cannons were classified, which had been described as 12 pounders or 24 pounders, rather than the caliber as other firearms are classified as today (ex. 155mm, 105mm, 88mm.) Listing of the common shotgun gauges:
.410—the odd one out in the shotgun line-up, it’s measured in diameter instead of weight. This is the smallest option for a shotgun favored by younger shooters for its forgiving nature and low recoil (the spring back from the force when fired) and popular shell size. This is not the best for home defense use, even for young shooters. It’s best suited as a small sporting shotgun for shooting at fowl and small game.
28 gauge—probably the least used gauge. Has the same uses as the .410 for sporting purposes
20 Gauge—packs a punch with a lighter spring back than a 12 Gauge. Suitable for a home defense application for the young/ diffident user and still has a variety of shell options, although not as much as the 12 gauge.
16 Gauge—the mid-point between the lighter feel and recoil of the 20 gauge and the power of the
12 gauge. This was more popular in the first half of the 20th century mainly as a bird gun. Not ideal as a home defense weapon due to the low selection of shells and because most designs are single shot guns.
12 Gauge—The shotgun of choice for home defense needs. The majority of shell sales are for 12 gauge shotguns. This gauge has been the favorite for militaries, police departments and citizens for over a century. It has the most variety of gun styles, shell options and accessories
Henceforth, the information given will be in reference to the 12 gauge.
10 gauge—although a bigger barrel, it’s not necessarily a more powerful option and not as common now a days mainly due to its bulkiness and overall weight. Although these types of shotguns do have their purpose, they aren’t appropriate as a weapon for the home.