A '''shotgun slug''' is a heavy barrel.  Much later shotguns were produced with rifled barrels, and slugs were designed to be fired from them with spin stabilisation. As these specialised "shotguns" were far more accurate than a smoothbore gun, they also usually featured greatly improved sights.  Many of these slugs use saboted sub-caliber projectiles, resulting in greatly improved external ballistics performance.

Some  less lethal shotgun ammunition is available in the form of slugs made of low-density material, such as rubber.  See  shotgun specialty ammunition for more information.

==Use==
Shotgun slugs are used to provide rifle-like performance from a shotgun, by firing a single large projectile rather than a large number of smaller ones.  In many populated areas, hunters are restricted to shotguns even for medium to large game, such as deer, due to concerns about the extreme range of modern rifle bullets.  In these locations, a slug will provide more range and far greater killing power than a load of buckshot.

Rifled slugs are often used by police equipped with riot shotguns.  Even out of a smoothbore barrel, the slugs will provide accuracy sufficient for antipersonnel use out to ranges about 100 yards (90 meters).  This allows the officer the ability to use the shotgun as a reasonable substitute for a rifle at medium ranges.

==Types==
The earliest shotgun slugs were just lead spheres, of just under the bore diameter, allowing them to pass through a choked barrel.  Often called ''pumpkin balls'', these slugs showed very poor accuracy, and were only effective at the very close ranges where they could be relied on to hit the target in a vital area.  Later types of slugs, the Brenneke and Foster slugs, used a weight-biased design and rifling-like fins to provide stability and the ability to easily compress and pass through a choked barrel.  These could be fired through a smoothbore barrel with reasonable accuracy, and significantly extended the effective range of the shotgun slug.  The latest improvement is the saboted slug, fired from a rifled shotgun barrel.  The saboted slug and rifled barrel combination provides even greater accuracy than the rifled slugs, and the slugs themselves are more aerodynamic, providing more range and a flatter trajectory.

===Brenneke Slugs===
thumb|right|250px|A 12 gauge Brenneke slug
The Brenneke slug was developed by the famous German gun and ammunition designer Wilhelm Brenneke (1865–1951) in 1898. The original Brenneke slug is a solid lead slug with fins cast onto the outside, much like a rifled Foster slug. There is  a plastic, felt or cellulose fiber wad attached to the base that remains attached after firing. This wad serves both as a gas seal and as a form of drag stabilization, much like the mass-forward design of the Foster slug. The "fins" impart little or no spin to the projectile; their purpose is to decrease the bearing surface of the slug to the barrel and therefore reduce friction and increase velocity.

Since the Brenneke slug is solid, rather than hollow like the Foster slug, the Brenneke will generally deform less on impact and provide deeper penetration (see terminal ballistics).  The sharp shoulder and flat front of the Brenneke mean that its external ballistics restrict it to short range use, as it does not hold velocity well.  The Brenneke slug in 12 gauge is well suited for large and dangerous game at close ranges, and deer sized game or antipersonnel use out to about 100 yards (90 meters).  Brenneke slugs are somewhat more accurate than the Foster slugs, but are usually more expensive.  With some new types of saboted Brenneke slugs, the range expands to 120-180 meters.

Brenneke slugs are loaded by a number of different makers (BRENNEKEUSA, FOB, ETC). Recently the Brenneke company, of Hanover, Germany, started marketing loaded ammunition, with Brenneke type slugs, saboted slugs, and buckshot.

===Foster Slugs===
A '''Foster slug''', invented by Karl Foster in 1931, is a type of shotgun slug designed to be fired through a smoothbore shotgun barrel.  

The defining characteristic of the Foster slug is the deep hollow in the rear, which places the drag will tend to push the slug back into straight flight.  This gives the Foster slug stability and allows for accurate shooting out to ranges of about 75 yards (about 70 meters).  Most Foster slugs also have "rifling", which consists of thin fins on the outside of the slug.  Contrary to popular belief, these fins actually impart no spin onto the slug as it travels through the air.  Since the slug is fired at a supersonic velocity, the nose of the slug pushing a shockwave creates a vacuum on the side of the slug, where the fins are located.  The actual purpose of the fins is to allow the slug to safely be swaged down when fired through a choke, although accuracy will suffer when such a slug is fired through tighter chokes.

It is also possible to fire Foster slugs through rifled slug barrels, though lead fouling (build-up in the rifle grooves) can be a problem.

thumb|right|250px|Pocisk typu Brenneke
'''Breneka''' albo '''Brenneke''', ciężki broni gładkolufowej. Podstawowym przeznaczeniem pocisków Brenneke jest polowanie na jelenie lub inną dużą zwierzynę, choć ze względu na swoją konstrukcję jest to pocisk stosunkowo mało precyzyjny, stosowany do strzelania na krótkich dystansach (do ok. 90 m). Do niemalejącej wśród myśliwych popularności breneki przyczynia się jej wysoka efektywność i precyzja przy dystansach nieprzekraczających 70 m, uniwersalność (możliwość użycia śrutu bez potrzeby zmiany broni) oraz względnie przystępne ceny. 

Skośne bruzdy na ściankach pocisku Brenneke ułatwiają przejście pocisku przez czok lufy (zwężenie lufy) w myśliwskiej broni śrutowej. Żebra pomiędzy bruzdami zostają w czoku spłaszczone, zmniejszając kaliber pocisku, a zatem i tarcie, i umożliwiając mu opuszczenie lufy. Dość powszechne przekonanie, że celem bruzd jest nadanie brenece obrotu w czasie lotu i poprawienie w ten sposób celności strzału, jest niesłuszne. 

Pociski tego typu mają także zastosowanie militarne, np. do odstrzeliwania zamków w drzwiach. Ponadto używa się ich w niektórych krajach jako ładunek strzelb policyjnych przy tłumieniu rozruchów ulicznych, co przy średnich dystansach pozwala zastąpić groźniejszy w skutkach karabin. Ze względu na dużą masę tego pocisku, a zatem i pęd po jego wystrzeleniu, który z powodu stosunkowej nieforemności (spłaszczony czubek) jest bardzo szybko wytracany po uderzeniu w cel, trafienie tym pociskiem powoduje zazwyczaj bardzo poważne obrażenia. Z drugiej strony, ponieważ jest to pocisk pełny, który nie deformuje się łatwo po uderzeniu w cel, więc ma on o wiele większą zdolność penetracji, a zatem niesie wyższe prawdopodobieństwo poważnych obrażeń wewnętrznych. Masa pocisku z naboju '12 gauge to około 32 gram, prędkość wylotowa to około 400m/s. 