Smoothbore refers to a firearm which does not have a rifled barrel. Rifling imparts a spin to the projectile, which stabilizes it and prevents it from tumbling. Early firearms did not have rifling, and had to fire spherical projectiles, so the random tumbling impacted the accuracy as little as possible. But because of the Magnus effect even a relatively smooth sphere will curve when rotating on any axis not parallel to the direction of travel. In the 18th century, the standard infantry arm was the smoothbore musket; by the 19th century, rifled barrels became the norm, because they could fire elongated projectiles, which provided better external ballistics. Some firearms A firearm is a kinetic energy mechanical device that fires either single or multiple projectiles propelled at high velocity by the gases produced by action of the rapid confined burning of a propellant. ... Rifling refers to spiral grooves that have been formed into the barrel of a firearm. ... The Magnus effect is the name given to the physical phenomenon whereby an objects rotation affects its path through a fluid, in particular, air. ... (17th century - 18th century - 19th century - more centuries) As a means of recording the passage of time, the 18th century refers to the century that lasted from 1701 through 1800. ... muskets and bayonets aboard the frigate Grand Turk A musket is a muzzle-loaded, smooth-bore long gun. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... External ballistics is the part of ballistics that refers to the behavior of a bullet after it exits the barrel and before it hits the target. ...

Some firearms are still made smoothbore. The most common of these is the shotgun. Firing multiple, non coaxial projectiles out of a rifled barrel would result in an "O" shaped pattern, with a very rapid spread, a high projectile density on the periphery, and a low projectile density in the interior. This is the exact opposite of the desired even distribution, with a fairly even number of pellets across a carefully expanding region. A pump-action and two semi-automatic action shotguns and boxes of ammunition A shotgun is a firearm typically used to fire a number of small spherical pellets, the shot, from a smoothbore barrel of relatively large diameter. ...

The other type of smoothbore that has come into use over the last part of the 20th century is the tank gun. Practical rifling can only stabilize projectiles of a certain length to diameter ratio. To reliably penetrate the thick armor of modern armored vehicles, a very long, thin kinetic energy projectile is required—too long to stabilize with rifling. These round are instead formed into a dart shape, using fins for stabilization (see kinetic energy penetrator for information on how this works). With the fins for stability, rifling is no longer needed and in fact the spin imparted by rifling will degrade the accuracy of a finned projectile. Because of the increasing use of the highly effective kinetic energy penetrator projectiles by tank guns, most modern tanks have smoothbore barrels. The russian navy also experimented with smoothbore large caliber navy guns, but funding cuts halted the progress. Panzerkampfwagen IV with long-barrelled gun ISU-122 A tank gun is the main armament of a tank. ... Dart may mean: Look up Dart on Wiktionary, the free dictionary A dart is a type of missile thrown or shot. ... A kinetic energy penetrator, long-rod penetrator, or armour-piercing fin-stabilized discarding sabot (APFSDS) is a type of ammunition which, like a bullet, does not contain explosives, but uses kinetic energy to penetrate the target. ...