OK, after all the chat about shotguns in
Quake and calling shotgun in the
car, some information about
real shotguns.
A shotgun is a gun, usually smooth-barrelled: this is what makes it different from a rifle.
Shotguns can be double-barrelled (typically used for hunting, but also for skeet shooting): when they are single-barrelled, they usually feed from a fixed tubular magazine under the barrel.
There are also shotguns that use a round drum-shaped magazine - the only one I am aware of is the Pancor Jackhammer, designed with military application in mind.
Shotguns come in different bore diameters, identified by two systems, the arcane and disturbing gauge, where a 10 gauge is bigger than a 12 gauge (which would be your standard shotgun), and the slightly-more-reasonable caliber, which gives the bore diameter in inches: a common one is .410.
Gun nuts, erm, RBKA-enthusiasts, also want me to write that a shotgun also has a choke, that's to say a tightening of the barrel: this influences shot dispersion, which will be discussed later.
Ammunition
The typical ammo for a shotgun is lead shot, that's to say lead
balls. Some specialized applications use
steel shot, or even
cubic shot.
The shot, which is by the way the part that flies out of the barrel and kills the white fluffy rabbit (or the evil masked perpetrator or the little flying clay disk), is contained in a plastic shell.
The shot is propelled by a charge, also contained in the shell. Between shot and charge there is something called a patch; usually taking the form of a little plastic cup or felt disk, its function is to seal the expanding gases in the barrel behind the shot, in order to maximize energy transfer from the charge to the shot.
What is missing ? The primer, that's to say a small amount of sensitive explosive that sits on the very bottom of the shell. The shotgun hammer strikes the primer, that explodes and in turn ignites the charge.
Lead shot comes in different calibers, that's to say, it can be either a bunch of small caviar-like balls, or a few big balls, like buckshot (which, by the way, can also take the form of cylindrical pellets). Of course, this too produced an arcane lexicon and measurement system, of which I know squat.
Shot comes out of the shotgun in one mass, but it then proceeds (due to air friction) to spread in a more or less cylindrical pattern. Different kinds of shotguns and barrels produce different patterns. In Italian, the pattern is called rosa, that's to say rose, which I find strangely poetic.
Notice, though, that shotguns can also fire slugs, incendiary rounds, flechette rounds and other exotic shotgun ammo, like the saboted slug (same idea as some types of tank ammo).
Deer hunters, for example, will use slugs to bring down their quarry.
Why use a shotgun with a slug instead of a rifle, one asks. I am told that a shotgun slug is much bigger (and thus heavier and thus more effective) that anything your typical rifle may shoot. Now that I think of it, I seem to remember that a 12 gauge slug is about a half inch in diameter, just like a .50 bullet. But a shotgun is much more convenient than a .50 rifle.
Consider also that the rifle has a big advantage in accuracy on long shots - but if you are hunting in a wood, you rarely have need for that accuracy. Thus the slug.
Additionally, and I have Razhumikin to thank for this info, a shotgun slug has a much shorter range than a rifle bullet. This is an advantage when hunting in high density areas, as it reduces the chance of accidents; actually, in Illinois it is illegal to hunt deer with rifles.
Applications
Shotguns are used in hunting small, flighty game where their shot dispersion property is very useful. When I was a kid I wondered just
how could someone hit a randomly flying small bird at 30 meters with a solid bullet - well, it turns out that you don't even try: you just use a lot of small shotgun pellets and hope for the best.
Shotguns are also used in home defense, because they are "easier" to aim than rifles or handguns, and also because small shot will stop a human being (even kill him at short distance), but it usually will not penetrate the flimsy walls prevalent in modern USA buildings.
There are some military applications of shotguns, but their limited range makes them a specialized device: I have seen them in the hands of a Marine boarding team.
There is also non-lethal ammunition (for riot situations) in the form of bean-bag rounds or baton rounds. Of course and despite its name, non-lethal ammunition can occasionally kill.
There is also target shooting, in the form of trap and skeet shooting.
Makers
Ah,
Beretta,
Browning,
Ithaca,
Rossi,
Benelli ... and a gazillion more.
Some shotguns are real works of art, hand-chiseled with hunting scenes.
Dangerous ?
Why, yes, of course, a
shotgun is fucking dangerous as most guns (excluding chocolate guns) are. Your typical 12 gauge shotgun can reliably kill at 10 meters. Closer up it will dig a
big hole through your chest or basically
behead you. Farther away,
lethality decays but not that fast. It also depends on the
caliber: small pellets slow down faster.
Shotguns are easy to underevaluate, because, well, they look less dangerous than an M16, and some people simply associate them with hunting.
But they are real guns, and as such they should be treated with the proper respect and fear.
Thanks to the readers who sent additional info and corrections.