Shotgun

From Wolfekipedia

A firearm designed to fire shells containing multiple round pellets (shot) rather than a single bullet.

Specific characteristics of shotguns are:

• Smooth, non-rifled barrels
• Large bore size (to allow a large number of projectiles to fit in each shell)

Common shotgun calibers

The bore size of a shotgun is called "gauge". The gauge of a shotgun is determined by a rather archaic system dating back to early cannon development. If one were to make lead balls the exact diameter of the inside of the shotgun barrel, that gauge of the gun would be the number of balls that could be made from exactly one pound of lead.

The most common shotgun calibers are 12 gauge (roughly .72 caliber) and 20 gauge (roughly .65 caliber). A close third place is .410 (this is an exception to the above sizing rule, and is called by its caliber rather than a gauge measurement). Less common, but still in use are 10 gauge (.78 gauge), 16 gauge (.66 caliber) and 28 gauge (.55 caliber).

Shot pattern

If you fire a shotgun shell at a paper target, the resulting set of holes is called a pattern. As the range increases, the pattern will grow larger, as the pellets spread out. Two important pieces of information a pattern can give you are the spread between the pellets farthest from each other (ie, how big of an area will be hit) and how much space there can be between pellets (ie, how large of an object could be inside the pattern but not be hit by any pellets).

Chokes

In order to improve long-range accuracy, shotgun barrels actually constrict slightly at the muzzle. This helps keep the shot pellets grouped more tightly together. The amount of constriction varies, and is called the gun's "choke". From least to most constrictive, the standard chokes are:

• Cylinder (no constriction)
• Improved, aka Improved Cylinder (0.10" constriction in 12ga)
• Modified (0.20" constriction in 12ga)
• Full (0.30" constriction in 12ga)

These chokes can be either permanently built into the barrel, or can be interchangeable (usually by way of threaded inserts in the muzzle for different chokes). Generally, double-barreled shotguns with permanent chokes will have a different choke on each barrel, so that one is best for short range and one for longer range.

12 Gauge shotgun shells

Shotgun shells come in many varieties, depending on the number and size of shot they contain. From smallest to largest, they are #12 birdshot up to #2 birdshot, then BB, then #4 buckshot to #1 buckshot, then #0, #00, and #000 buckshot.

The smallest commonly used shot size is #8 birdshot. A #8 shell contains about 410 pellets of 0.089" diameter. No typo, that really is 400 pellets in each shell. These shells are generally used for shooting clay pigeons, since they are delicate and easily broken - the large number of pellets makes for a denser pattern, and less chance of having a clay inside the pattern but not hit. These shells are also used for small birds, for the same reasons. This size of shot is the cheapest shotgun ammunition available, and good for practice. Shells of #9 and #7.5 are interchangeable with #8 for most applications.

The next common size of shot are #6, #4, and #2 birdshot. These use:

• #6 bird: 225 pellets of 0.109" diameter
• #4 bird: 135 pellets of 0.129" diameter
• #2 bird: 90 pellets of 0.148" diameter

These sizes are used for hunting birds and small game. The larger the animal hunted, the larger the appropriate shot, to ensure a hit will kill the animal rather than just wound it.

Next up, we have #4 buckshot. This is the smallest size designated as "buck", and it uses 21 pellets of 0.24" diameter. While the name implies hunting deer, this is not a common practice - rifle cartridges or shotgun slugs are much more practical for hunting medium game than buckshot.

Next is #1 buckshot, with 11 pellets of 0.30" diameter. This is not a size you will often see, but I include it because it is objectively the most effective size for defensive use against humans, according to the very knowledgeable folks at Firearms Tactical.

Lastly, we have the very well-known #00, or double-ought buck. In a standard load, this consists of 9 pellets of 0.33" diameter, and is readily available. Double ought is by far the most common shot size chosen for use against humans, and is the choice of most military forces that use shotguns. Each shell is approximately the same as nine simultaneous shots of .32 ACP pistol ammunition.

In 20 gauge and others, these shot sizes will be similar. The number of pellets will change (since the shells themselves have less volume for pellets), and some large shot sizes will not be available. For more specific advice on shot sizes to use on specific game, see Remington's Guide

Shotgun slugs

A final type of shotgun ammunition is the single slug. This shell contains, as you might suspect, one projectile which is the full diameter of the bore. Basically, it turns a shotgun into a very large-caliber rifle. In many areas, hunting with rifles is prohibited (due to population density issues), and shotgun slugs are a common substitute.

As you may recall, shotgun barrels are not rifled. This makes for a much less accurate projectile than a rifle would fire, but there are several solutions. The first is the design of the slug itself. Rather than being just a round ball, modern slugs (like the Foster and Brenneke types) are disigned to be drag-stabilized, like a badmitton birdie. These are sometimes called "rifles slugs", as they often have what appears to be rifling cut into the slug itself. However, that feature does not actually give the slug any added accuracy - though it does allow the slugs to compress somewhat, and be fired through shotguns with constrictive chokes.

The other solution to slug accuracy is to replace the smoothbore shotgun barrel with a rifled one, and use slugs in sabots. The rifling spins the sabot as the slug moves down the barrel, and the sabot in turn spins the slug. This works fairly well, and can at best allow 3.5" or 4" groups at 100 yards. However, the rifling also tends to make regular shot spread out is a wide donut-shaped pattern, rendering it much less effective.

Slugs are quite heavy, but have fairly low muzzle velocities, resulting in short effective ranges. Even when zeroed at 50 yard, most slugs will be 5 inches or more low by 100 yards, and drop quickly thereafter.