A long gun is a category of firearms and cannons with longer barrels than other classes. In small arms, a long gun is designed to be fired braced against the shoulder, in contrast to a handgun, while in artillery a long gun would be contrasted with a howitzer or carronade.
Small arms 
The actual length of the barrels of a long gun are subject various laws in many jurisdictions, for example by the National Firearms Act in the United States, which sets a minimum length of 16 inches (40 cm) for rifle barrels and 18 inches (45 cm) for shotgun barrels. Canada has a limit of 18.5 inches (47 cm) for either. In addition, Canada puts a minimum fireable length for long guns with detachable or folding stocks of 26 inches (66 cm). In the United States, the minimum length for long guns with detachable or folding stocks is 26 inches (660 mm) with the stock in the extended position.
Advantages and disadvantages of long guns 
Almost all long-arms have front grips (forearms) and shoulder stocks, which provides the user the ability to hold the firearm more steadily than a handgun. In addition, the long barrel of a long gun usually provides a longer sight plane for iron sights, providing the user with more precision when aiming. The presence of a stock makes the use of a telescopic sight or red dot sight more practical than with a hand gun.
The mass of a long gun is usually greater than that of a short gun, making the long gun more expensive to transport, and more difficult and tiring to carry. The increased moment of inertia makes the long gun slower and more difficult to traverse and elevate, and it is thus slower and more difficult to adjust the aim. However, this also results in greater stability in aiming. The greater amount of material in a long gun tends to make it more expensive to manufacture, other factors being equal. The greater size makes it more difficult to conceal, and more inconvenient to use in confined quarters, as well as requiring a larger storage space.
Shotguns are long guns that are designed to fire many small projectiles at once. This makes them very effective at close ranges, but with diminished usefulness at long range.
In historical navy usage, a long gun was the standard type of cannon mounted by a sailing vessel, called such to distinguish it from the much shorter carronades. In informal usage, the length was combined with the weight of shot, yielding terms like "long 9s", referring to full length cannons firing a 9-pound round shot.
See also 
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