Editing Smoothbore (section)

===Artillery and tanks===
The cannon made the transition from smoothbore firing [[Round shot|cannonballs]] to rifled firing [[shell (projectile)|shells]] in the mid-19th century.  However, to reliably penetrate the thick armor of modern armored vehicles many modern [[tank gun]]s have moved back to smoothbore. These fire a very long, thin [[kinetic energy penetrator|kinetic-energy projectile]], too long in relation to its diameter to develop the necessary spin rate through rifling. Instead, kinetic energy rounds are produced as fin-stabilized [[Dart (missile)|dart]]s. Not only does this reduce the time and expense of producing rifled barrels, it also reduces the need for replacement due to barrel wear.{{cn|date=January 2023}}

The armour-piercing gun evolution has also shown up in small arms, particularly the now abandoned U.S. [[Advanced Combat Rifle]] (ACR) program.  The ACR "rifles" used smoothbore barrels to fire single or multiple [[Fléchette|flechette]]s (tiny darts), rather than bullets, per pull of the trigger, to provide long range, flat trajectory, and armor-piercing abilities.  Just like kinetic-energy tank rounds, flechettes are too long and thin to be stabilized by rifling and perform best from a smoothbore barrel.  The ACR program was abandoned due to reliability problems and poor [[terminal ballistics]].{{cn|date=January 2023}}

[[Mortar (weapon)|Mortar]] barrels are typically [[muzzle-loading]] smoothbores. Since mortars fire bombs that are dropped down the barrel and must not be a tight fit, a smooth barrel is essential. The bombs are fin-stabilized.