The blunderbuss is a muzzle-loading firearm with a short, large caliber barrel, which is flared at the muzzle, and used with shot. The blunderbuss is an early form of shotgun adapted to military and defensive use. The term dragon was used to describe a blunderbuss in handgun form, and it is from this that the term dragoon evolved.
The blunderbuss was an early form of shotgun, and served in similar roles. While fictional accounts often list the blunderbuss as being loaded with various scrap iron or rocks, this would result in damage to the bore of the gun; it was typically loaded with a number of lead balls smaller than the bore diameter. Barrels could be made of steel or brass, and the flare was not intended to increase the spread of the shot, but rather to ease in loading the gun. The flared muzzle is the defining feature of the blunderbuss, differentiating it from large caliber carbines; the distinction between the blunderbuss and the musketoon is less distinct, as musketoons were also used with shot, and some had flared barrels. Blunderbuss were typically very short, with barrels under two feet (60 cm) in length, at a time when a typical musket barrel was over three feet (90 cm) long. One source, describing arms from the early to middle 17th century, lists the barrel length of a wheel lock dragon is around eleven inches (28 cm), compared to a sixteen inch (41 cm) length for a blunderbuss.
The blunderbuss, and especially the shorter dragon, was typically issued to troops such as cavalry, who needed a lightweight, easily handled firearm. The dragon became so associated with cavalry and mounted infantry that the term dragoon (French dragon, carbine, "fire-breather", from Old French, dragon, dragon, from Latin dracō, dragon, serpent, from Greek δράκων (drákōn), "serpent of huge size, python, dragon") became synonymous with mounted infantry. In addition to the cavalry, the blunderbuss found use for other duties in which the shotgun-like qualities were desirable, such as for guarding prisoners or defending a mail coach, and its use for urban combat was also recognized.
The blunderbuss used by the British mail service during the period of 1788 - 1816 was a flintlock with a 14 inch long flared brass barrel, brass trigger guard, and iron trigger and lock. A typical British mail coach would have a single postal employee on board to guard the mail from highwaymen, armed with a blunderbuss and a pair of pistols. One 18th century coaching blunderbuss in another British collection had a brass barrel 17 inches long, flaring to 2 inches at the muzzle; it was also provided with a spring-loaded bayonet which was held along the barrel by a catch, and would spring forward into place when released.
While the blunderbuss is often associated with the Pilgrims, evidence suggests that the blunderbuss was relatively scarce in the American colonies. After the Battle of Lexington, British General Thomas Gage occuped Boston, Massachusetts. After negotiating with the town committee, Gage agreed to let the inhabitants of Boston leave town with their families and effects, if they surrendered all arms. While most of the residents of Boston stayed, those who left under the agreement surrendered 1778 firearms, 634 pistols, 273 bayonets, and only 38 blunderbusses. The blunderbuss did still have its civilian applications, however; the Lewis and Clark Expedition carried a number of blunderbusses, some of which were mounted and used as small swivel guns on the pirogues.
By the middle 19th century, the blunderbuss was considered obsolete. The blunderbuss was replaced in military use by the carbine, though the latter was considered by some to be a poor replacement (the carbine in use by the British during the Crimean War was lampooned in Punch as being able, in the hands of a good shot, to "hit a haybrick at 80 yards"), though it still found use with civilians as a defensive firearm.