1. barrel
   chamber
2. trigger

Basic firearms blast projectiles through a barrel toward a target. On sidearms, the barrel is quite short; on a large rifle, the barrel might measure a few feet in length.

1. white powder
   black powder
2. red powder

Black gunpowder reigned in the early days of firearms and up to the 19th century. Then, gun makers began using cleaner and more powerful propellants.

1. color
   trigger length
2. bore diameter

Modern guns, like many rifles and pistols, are categorized by caliber, which refers to bore diameter. The bigger the bore, the bigger the bullet and the more powerful the punch.

1. feet or yards
   millimeters or inches
2. miles or kilometers

Manufacturers note caliber (bore diameter) in millimeters or inches. So, you'll often see figures like 9mm or .357 (in.) in reference to firearm size.

1. grooved barrel
   laser sight
2. magnum shells

Rifles have rifled (grooved) barrels that cause protectiles to spin as they emerge from the muzzle. The spinning motion makes the bullet travel in a more predictable (i.e. accurate) path.

1. shotgun
   pistol
2. machine gun

In shotguns, "gauge" refers to the bore diamater of the gun. The 12-gauge shotgun is a very popular size, suited to both hunting and self-defense.

1. China
   Guatemala
2. Brazil

In the 1200s, the Chinese created hand cannons, which were just metal tubes with gunpowder. They were crude but effective in close-quarters combat.

1. shotgun
   handgun
2. rifle

Handguns, or sidearms, are the smallest guns. They come in all sorts of shapes and sizes, from those that are easily concealed, to mammoth versions that require two hands to shoot.

1. nuclear
   ranged
2. melee

In terms of categorization, firearms are a type of ranged weapon. That just means they can be used to attack targets that are out of arm's reach.

1. howitzer
   shotgun
2. handgun

Revolvers are handguns with a single barrel matched to spinning (revolving) chambers. Those chambers let the shooter loose multiple shots before reloading.

1. to prevent accidental discharge
   to load, fire, and eject spent cartridges
2. to aim

A gun's "action" is the system that loads, fires, and then ejects spent cartridges or shells. The action may be a simple as "single-shot" or fully automatic.

1. firing mechanism
   accuracy
2. safety

Gun makers have devised all sorts of firing mechanisms in the past few centuries. In a percussion lock (or caplock) weapon, a hammer strikes a percussion cap, which then blasts the charge.

1. just once before reloading
   as fast as you can pull the trigger
2. 20 rounds per second

Semi-auto firearms are exceedingly popular and include guns like revolvers. They shoot as fast you can work the action.

1. rifle
   smoothbore
2. both

Very large smoothbore guns or rifles are sometimes called elephant guns, because they're powerful enough to take down large game. They often deliver major recoil, too.

1. They are fully automatic.
   They use only tracer rounds.
2. They include loudspeakers used to taunt enemy soldiers.

In the mid-1800s, gun designers began tinkering with fully automatic weapons like machine guns. By the end of the century, they'd devised numerous variants, some of which were capable of spewing hundreds of rounds per minute.

1. larger caliber
   shorter barrel
2. rocket launcher included

A carbine is a a rifle with a shorter-than-normal barrel. They are often used by soldiers, who find full-size rifles unwieldy in the heat of close-quarters combat.

1. .410
   12 gauge
2. 36 gauge

The 12 gauge shotgun is a common firearm for waterfowl and upland hunting. It packs enough power to kill birds cleanly dozens of yards away.

1. it fires pistol caliber cartridges
   it's smaller than a regular machine gun
2. there is no difference

Sub-machine guns fire pistol caliber cartridges, while machine guns fire full caliber or intermediate cartridges.

1. pistol
   flamethrower
2. shotgun

The pump-action shotgun is very common. To make it work, the shooter pulls a grip on the weapon's fore end and then pulls -- this action ejects a spent shell and then loads a new one.

1. They used matches.
   They used their teeth.
2. They used gasoline.

Old matchlock guns emerged in the 1400s, and they were as primitive as they sound -- soldiers touched a bit of burning twine or a match to light powder in the flash pan. As you can imagine, it was difficult to aim the gun while also attempting to ignite the powder.

1. It shoots flames on command.
   It can shoot in automatic or semi-automatic mode.
2. It shoots either Communists or fascists.

Some machine guns are equipped with a selective fire switch. This switch means the weapon can fire in full automatic or semi-automatic mode.

1. 250 yards
   800 yards
2. more than a mile

Skilled snipers can hit targets that are thousands of yards away. In ideal conditions, they might hit the bullseye more than a mile and a quarter from their shooting position.

1. lever action
   single shot
2. full auto

In the late 1800s, gun makers began creating lever-action rifles, which worked much more quickly than old single-shot rifles. The Winchester Model 1873 was very popular in the Wild West, where it was used by soldiers and big game hunters.

1. tip of the trigger
   top of the sight
2. end of the barrel

The muzzle is the very end of the barrel -- in the words, the part you should never point at anything you don't intend to destroy. Early weapons were mostly the "muzzleloader" variety, meaning the bullet was rammed from the muzzle down to the chamber.

1. pistol
   shotgun
2. rifle

In the 1870s the Colt Single Action Army was an incredibly popular revolver in the Old West. It was also commonly known as the "Peacemaker."

1. true
2. false

Muskets were some of the earliest firearms, but they were smoothbore, not rifled. All primitive muskets and rifles were loaded through the muzzle.

1. a high-powered machine gun
   a tiny pistol
2. a bazooka

The minigun is a lethal rotary machine gun. It's equipped with a motor that spins the barrels and is capable of unleashing not hundreds -- but thousands -- of rounds per minute.

1. brass
   iron
2. fairy dust

At the end of the 1800s, gun makers finally combined powder and lead into what was called a "cartridge," a paradigm shift that made loading much easier. Most cartridges have brass casings.

1. pistol
   rifle
2. machine gun

In the late 1880s, a man named Hiram Maxim devised the Maxim machine gun, which harnessed recoil energy to eject spent cartridges. The Maxim gun could shoot hundreds of rounds per minute, and it was used to decimate numerous unsuspecting enemy forces.

1. black powder brand
   target impact
2. projectile propulsion

Every firearm has slightly different internal ballistics, the properties that fuel projectile propulsion. Gunsmiths must be experts of internal ballistics in order to make safe and accurate weapons.