Trapdoor actions The earliest metallic-cartridge breechloaders designed for general military issue began as conversions of muzzle-loading rifle muskets. The upper rear portion of the barrel was filed or milled away and replaced by a hinged breechblock which opened upward to permit loading. An internal angled firing pin allowed the re-use of the rifle's existing side-hammer. The
Allin action made by Springfield Arsenal in the US hinged forward; the
Snider–Enfield used by the British opened to the side. Whereas the British quickly replaced the Snider with a dropping-block Peabody-style Martini action, the US Army felt the trapdoor action to be adequate and followed its muzzleloader conversions with the new-production
Springfield Model 1873, which was the principal longarm of the
Indian Wars and was still in service with some units in the
Spanish–American War. Other trapdoor actions include the rare Confederate
Tarpley carbine, the Austrian
Wanzl, the Belgian
Albini-Braendlin rifle and
Terssen conversion (some of which were made from French 1777 pattern flintlocks), the M1842/59/67 Swiss Milbank-Amsler, the M1859/67 Spanish Berdan, and the Colt-manufactured Russian
Berdan Type I. All of these designs save the 1863 Tarpley date from the period 1865–1869, and all but the Tarpley and the Russian Berdan were conversions from muzzle-loaders.
Break actions Perhaps the most common type of single-shot action, usually found in shotguns, small pistols, and black-powder "elephant" guns, a break action connects the barrel assembly to the breechblock with a hinge. When a locking latch is released, the barrel assembly pivots away from the receiver, opening the breech and sometimes on higher quality firearms, partially extracting the spent cartridge.
Rolling block actions In a rolling block action, the breechblock takes the form of a part-cylinder, with a pivot pin through its axis. The operator rotates or "rolls" the block to open and close the breech; it is a simple, rugged and reliable design. Rolling blocks are most often associated with firearms made by
Remington in the later 19th century; in the Remington action the hammer serves to lock the breech closed at the moment of firing, and the block, in turn, prevents the hammer from falling with the breech open. An interesting variation of the rolling block was the Austrian
M1867 Werndl–Holub, in which the pivot pin was parallel to the barrel and the block rotated sideways.
Dropping block actions These are actions wherein the breechblock lowers or "drops" into the receiver to open the breech, usually actuated by an underlever. There are two principal types of dropping block: the tilting or pivoting block and the falling or sliding block.
Tilting block actions In a tilting or pivoting block action, the breechblock is hinged at the rear (in contrast with
tilting bolt, which is not hinged). When the lever is operated, the block tilts down and forward, exposing the chamber. The best-known pivoting block designs are the Peabody, the Peabody–Martini, and
Ballard actions. The original Peabody rifles, manufactured by the Providence Tool Company, used a manually cocked side-hammer. Swiss gunsmith Friedrich Martini devised an action that resembled the Peabody but incorporated a hammerless striker cocked by the operating lever with the same motion that pivoted the block. The 1871
Martini–Henry which replaced the "trapdoor" Snider–Enfield was the standard British Army rifle of the later Victorian era, and the Martini was also a popular action for civilian rifles. Charles H. Ballard's self-cocking tilting-block action was produced by the
Marlin Firearms Company from 1875 and earned a superlative reputation among long-range "Creedmoor" target shooters. Surviving Marlin Ballards are today highly prized by collectors, especially those mounted in the elaborate Swiss-style
Schützen stocks of the day.
Falling block actions In a falling or sliding block action the block does not pivot but rather slides vertically in a slot milled into the receiver. Falling blocks are among the strongest small-arm actions ever produced, and are also used in heavy artillery. Well-known falling block designs include the
Sharps rifles and carbines, the
Browning/Winchester Single Shot, the
Farquharson rifle, and the modern
Ruger No. 1.
Bolt-actions Although bolt-actions are usually associated with fixed or detachable box magazines, in fact, the first general-issue military breechloader was a single-shot bolt-action: the paper-cartridge
Prussian needle gun of 1841. France countered in 1866 with its superior
Chassepot rifle, also a paper-cartridge bolt-action. The first metallic-cartridge bolt-actions in general military service were the
Berdan Type II introduced by Russia in 1870, the
Mauser Model 1871, and a modified Chassepot, the
Gras rifle of 1874; all these were single-shots. Today most top-level smallbore match rifles are single-shot bolt-actions. Single-shot bolt-actions in .22 caliber were also widely manufactured as inexpensive "boys' guns" in the earlier 20th century; and there have been a few single-shot bolt-action shotguns, usually in .410 bore.
Other single-shot actions •
The Ferguson rifle: British Major Patrick Ferguson designed his rifle, considered to be the first military breechloader, in the 1770s. A plug-shaped breechblock was screw-threaded so that rotating the handle underneath would lower and raise it for loading with ball and powder; the flintlock action still required conventional priming. •
The Hall rifle: The United States' first breechloading cavalry carbine, the Hall was introduced in 1819. The lever tipped the breechblock including the chamber upwards and back, allowing it to be loaded with powder and ball without the inconvenience of loading and ramming from the muzzle. Originally flintlocks, Halls later were made as or converted to percussion locks. •
The Kammerlader: A crank-operated Norwegian firearm produced around the time of the Prussian Needle-gun. Originally used a paper cartridge. Later many were converted to rimfire. •
The Burnside carbine: Invented by future-general
Ambrose Burnside in 1857, this percussion-cap carbine became the third-most common cavalry breechloader in the Civil War after the Sharps and Spencer. Essentially a modification of the Hall concept, the Burnside featured a unique conical cartridge with a crushable hollow front rim, designed to seal the breech on closing. •
The Rising breech carbine: An unusual action produced by Bilharz, Hall and Co. for the southern
Confederacy, the rising breech's underlever caused the breechblock including the chamber to slide vertically above the line of the barrel, the reverse of a falling-block; the chamber was loaded from the front with a paper cartridge. •
The Morse Carbine: Its action is similar to the Hall rifle but the shape of its chamber is different. •
Winchester Model 55: An unconventional hybrid of a single-shot and a
semi-automatic, this .22-caliber rifle ejected the fired case and recocked itself like a conventional
blowback-operated self-loader, but it lacked a
magazine and had to be manually reloaded for each shot. • "'Screw Barrel Actions'": The OSS stinger pen pistol and several other clandestine pen guns, as well as homemade zip guns often made using plumbing parts, and cane guns used for both defense and poaching use a screw thread to attach the chambered barrel to a receiver with some sort of breech and firing pin. The user unscrews the barrel from the receiver to expose the chamber to load a cartridge. The RN50 .50 BMG single-shot rifle uses a similar screwthread breech cap to allow an otherwise simple break-action to contain a
.50 BMG cartridge. ==Modern single-shots==