Not a firearm but a gun that uses compressed air or CO2 to propel a projectile. Examples: BB gun, pellet gun, CO2 gun. More

The AKS-74U is the work of Russia's most famous weapons designer, Mikhail Kalashnikov. As its name implies (U stands for ukorochennyj or "shortened") it's a short-barreled variant of the folding-stock AKS-74 assault rifle issued to airborne troops.

The 74U was developed to fill a Soviet Army need for an ultra compact weapon. While the addition of a side-folding stock to the standard AK-74 reduced the weapon's overall length considerably, even this was still too long for use by certain specialists such as drivers of combat vehicles and special law enforcement sub-units. More

This generally refers to the assembled components of complete cartridges or rounds i.e., a case or shell holding a primer, a charge of propellant (gunpowder) and a projectile (bullets in the case of handguns and rifles, multiple pellets or single slugs in shotguns). More

By federal definition, a firearm manufactured prior to 1898 or any replica of any firearm if it is not designed or redesigned for using rimfire or conventiaonal centerfire fixed ammunition, or if it uses rimfire or conventional centerfire fixed ammunition which is no longer manufacturered in the US or is not readily available.

Also, andy muzzle loading rifle, muzzle loading shotgun, or muzzle loading pistol which is designed to use blaock powder or plack powder substitude and which cannot use fixed ammunition. More

ArmaLite Division, Fairchild Engine and Airplane Corporation.
 
ArmaLite was first established as a Division of Fairchild Engine and Airplane Corporation on October 1, 1954.  At least two years of privately funded development preceded the Fairchild supported program.  The ArmaLite Division of Fairchild is the first phase of the company’s history.
 
There had been very little fundamental development in the small arms industry for more than fifty years.   Increasing military use of the machine gun and production of semiautomatic rifles were the main significan More

By federal definition, "a projectile or projectile core which may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper More

By U.S. Army definition, a selective-fire rifle chambered for a cartridge of intermediate power. If applied to any semi-automatic firearm regardless of its cosmetic similarity to a true assault rifle, the term is incorrect. More

Any weapon used in an assault (see weapon). More

see semi-automatic More

A firearm designed to feed cartridges, fire them, eject their empty cases and repeat this cycle as long as the trigger is depressed and cartridges remain in the feed system. Examples: machine guns, submachine guns, selective-fire rifles, including true assault More

A term used often to describe what is actually a semi-automatic pistol. It is, technically, a misnomer but a near-century of use has legitimized it, and its use confuses only the novice. More