A breech-loading swivel gun was a particular type of swivel gun and a small breech-loading cannon invented in the 14th century. It was equipped with a swivel for easy rotation and was loaded by inserting a mug-shaped device called a chamber or breech block, filled with gunpowder and projectiles. It had a high rate of fire, as several chambers could be prepared in advance and quickly fired in succession and was especially effective in anti-personnel roles. It was used for centuries by many countries of Europe, Asia and Africa.

Although breech-loading is often considered a modern innovation which facilitated the loading of cannons, breech-loading swivel guns were invented in the 14th century, and used worldwide from the 16th century onward by numerous countries, many of them non-European. They have been called by many names, sometimes "Murderer", "Base", "Sling", "Port-Piece", "Serpentine", "Culverin", "Pierrier", "Stock Fowler", and "Patterero" in English; "Pierrier à boîte" in French; "Berço" in Portuguese; "Verso" in Spanish; "Prangi" in Turkish; "Kammerschlange" (lit. "chamber snake", properly means "breech-loading falconet") in German; "Folangji" (佛郎机, from Turkish "Prangi" or Turkic "Farangi"), "Folangji chong" (佛郎机铳, Prangi or Farangi gun), "Fo-lang-chi p'ao" (佛朗机炮 or 佛朗機砲, Portuguese cannon) in Chinese; "Bulang-kipo" ("불랑기포[佛郞機砲]") in Korean; "Furanki" (仏郎機砲, "Frankish gun") or 子砲 ("Child cannon") in Japanese; and "Bedil" or "bḍil" (ꦧꦣꦶꦭ) in Javanese. Some of them were used until the 20th century.

Breech-loading swivel guns were developed surprisingly early, and were used from 1364 onward. The guns were loaded with mug-shaped chambers, in which gunpowder and projectile had been filled in advance. The chamber was then put in place, blocked with a wedge, and then fired. As the loading was made in advance and separately, breech-loading swivel guns were quick-firing guns for their time. An early description of a breech-loading swivel gun puts the weight of the gun at 118 kilograms (260 lb), equipped with three chambers for rotations, each 18 kilograms (40 lb) in weight, and firing a 280 grams (9.9 oz) lead shot. The guns had a disadvantage: they leaked and lost power around the chambers, but this was compensated by the high rate of fire as multiple chambers could be prepared in advance. Breech-loading swivel gun could fire either cannonballs against obstacles, or grapeshot against troops.

During the Middle-Ages, breech-loading swivel guns were developed by the Europeans also partly as a cheaper alternative to the very expensive bronze cast muzzle-loading cannons, as bronze was many times more expensive than iron. As cast iron was not yet technologically feasible for the Europeans, the only possibility was to use wrought iron bars hammered together and held with hoops like barrels. With this method, a one piece design was very difficult, and a fragmental structure, with separated chamber and barrel was then selected.

Around 1500, Europeans learnt how to cast iron, and shifted their cannon productions to one-piece iron muzzle-loaders. China started to adopt European breech-loading swivel guns from 1500 onward, limiting at the same time the production of their own muzzle-loaders, because of the high effectiveness of the breech-loading swivel gun as an anti-personnel gun, which to them was more interesting than the sheer power of a cannonball.

Usage of the breech-loading swivel gun continued in Europe however, with, as early as the 17th century, characteristics very similar to the modern machine-gun or mitrailleuse.

Breech-loading swivel guns were used to advantage at the bow and stern on warships, but were also used in fortifications.

Breech loading guns were used by Burgundians as early as 1364. The Portuguese had versos (Berços) in c. 1410, while England has a picture of port-pieces of 1417, although the picture itself was made c. 1485. The Ottomans used the prangi from the mid-15th century onwards in field battles, aboard their ships, and in their forts, where prangis often comprised the majority of the ordnance. These weapons would spread eastward to Indian ocean, eventually reaching Southeast Asia in c. 1460 AD.