The Colt Single Action Army handgun (also known as the Colt Peacemaker, Single Action Army or SAA, Colt .45 and sometimes as The Equalizer or Colt Peacekeeper) is a single action revolver with a revolving cylinder holding six rounds. It was designed for the US government service revolver trials of 1873 by Colt's Manufacturing Company and adopted as the standard military service revolver until 1892.
The Colt Single Action Army has been offered in over 30 different calibers and various barrel lengths. Its overall appearance has remained consistent since 1873. Colt has discontinued its production twice, but brought it back due to excessive demand. The pistol was popular with ranchers, lawmen, and outlaws alike, but current models are mostly bought by collectors and reenactors. Its design has influenced the production of numerous other models from companies such as the Great Western Arms Company, Ruger, Beretta, Freedom Arms, USFA, Cimarron, and Uberti.
The Colt Single Action Army was designed for the US government service revolver trials of 1873 by Colt's Manufacturing Company and adopted as the standard military service revolver. Its original moniker was the "New Model Army Metallic Cartridge Revolving Pistol".
The .45 Colt cartridge was of center fire design containing charges of up to 40 grains (2.6 g) of fine grained black powder and a 255-grain (16.5 g) blunt round nosed bullet. Relative to period cartridges and most later handgun rounds, it was quite powerful in its full loading.
The Colt Single Action Army handgun replaced the Colt 1860 Army Percussion revolver and remained the primary US military sidearm until 1892 when it was replaced by the Colt Model 1892, an enclosed frame double action revolver. By the end of 1874, serial no. 16,000 was reached; 12,500 US-Cavalry units chambered for the .45 Colt cartridge had entered service and the remaining revolvers were sold in the civil market. From 1875 until 1880 Colt marketed the Single Action in a separate number range from no. 1 to 1,863 in the .44 rimfire Henry caliber.
By the mid 1870s, the Army had purchased a significant number of Smith and Wesson revolvers chambering a shorter .45 round. Logistical problems arose because the ammunition was not interchangeable. The Colt revolvers would accept the shorter round but not vice versa. For a time, the Government stopped orders for the longer Colt cartridge and used the Smith and Wesson round exclusively.  Variations 1873- 1941
The Single Action Army became available in standard barrel lengths of 4¾", 5½" as well as the Cavalry standard, original 7½". The shorter barreled revolvers are sometimes called the "Civilian" or "Gunfighter" model (4¾") and the Artillery Model (5 1/2"). In practice, the customer could order just about any barrel length and combination of basic features and finish. In 1892, at serial number 144,000, a springloaded base pin latch replaced the cylinder pin retaining screw and by 1900, at serial number 192,000, the Colt Single Action was certified for use with smokeless powder. In 1920, larger, highly visible sights replaced the original thin blade and notch. The revolvers remained essentially unchanged from that point until cessation of manufacture at the beginning of World War II.  45 Colt cartridge variations Colt .45 Cartridges
The original .45 Colt black powder load of 40 grains propelled the 250-255 grain bullet at a nominal 970 feet per second (300 m/s). Authors John Taffin and Mike Venturino have demonstrated that modern black powder loadings of the 45 Colt cartridge frequently achieve velocities in the vicinity of 1,000 feet per second (300 m/s) with the 7-1/2" "cavalry" barrel length, even though modern solid-head cases make it impossible to load a full 40 grains. Specifications for 20th-century smokeless loads set velocity with a 255-grain (16.5 g) round-nosed flat-point bullet at 870 feet per second (270 m/s) providing 429-foot-pound-force (582 J) energy.
The current version of the 45 Colt differs from the original cartridge case in that the rim is significantly larger (with a groove immediately above it) and the internal aspect of the primer pocket is surrounded by solid brass instead of protruding into the powder chamber. This "solid head" case is stronger and resists deformation of the primer pocket. Some commercial and custom revolvers and single-shot pistols (such as the Ruger Blackhawk, T/C Contender and others) employ high-pressure loads that are dangerous in the Single Action Army and other vintage arms chambered for the 45 Colt cartridge, especially 19th-century "pre-smokeless" revolvers which should be fired (if at all) only with black powder or light smokeless loads.
Prior to World War II, the 45 Colt used a groove diameter of .454"; post-WW II production adopted the .452" groove diameter of the 45 ACP. Handloaders should slug their barrels to determine the correct groove diameter, and size cast bullets accordingly.  Calibers
By 1878 the Colt SAA was being offered from the factory in additional calibers for civilian and foreign military sales. Many were sold in .44-40 Winchester Center Fire (WCF), introduced in 1878 to allow cross-compatibility with the Winchester '73 lever action rifle (this model was called the "Frontier Six-Shooter" which was etched and later stamped on the barrel). Additional period calibers for the SAA included .38-40 Winchester (38 WCF) introduced in 1884, and the .32-20 Winchester (32 WCF) introduced in 1884 and the .41 Colt introduced in 1885. Some of the separately-serialized .44 Henry rimfire revolvers were rechambered to .22 rimfire after 1885. The SAA at one time or another was offered in dozens of calibers from .22 rimfire to .476 Eley, though the .45 Colt has always been the most common. A scaled-down .22 rimfire version called the Scout or Frontier Scout was available in the late 20th Century, and these guns now command high prices.  First, Second, Third Generation Colt Single Action and major calibers Factory engraved SAA by Cuno Helfricht, shipped 1893 to [link] & Co. Albuquerque NM
From 1873 through 1940 (with small numbers assembled during and after World War II, the so called "Pre-War, Post-War" model), production of colt single actions reached 357,859. This is identified as the "Pre War" or "First Generation" of the model. Calibers, at least thirty in all, ranged from .22 rimfire through .476 Eley with approximately half or 158,884 (including Bisley and Flat Top Target variations), were in the .45 Colt chambering. The next most prevalent were the .44-40 Winchester Center fire (WCF) at 71,392; 38-40 (38 WCF) at 50,520; 32-20 Winchester (32 WCF) at 43,284 and, the 41 Colt at 19,676.
Second Generation Colts were produced from 1956-1974 and carried serial numbers in the range of 0001SA to 73,205SA. The Third Generation began in 1976 characterized by a change in barrel thread pitch and a solid cylinder bushing replacing the removable/replaceable part from the first and second generations. This Generation ran until 1982 as a limited-issue product with the serial number range of 80,000SA to 99,999SA. In 1994, production resumed with the increase in popularity of "Cowboy Action Shooting". These models are known either as "Late Third Generation" or sometimes Fourth Generation with the serial number convention changing yet again starting with S02001A and continuing with the "S" prefix and "A" suffix to 2009. Colt currently offers the Single Action Army in one of two finishes: either an all-nickel or blued with color case-hardened frame; in the traditional three barrel lengths: 4-3/4", 5-1/2" and 7-1/2"; and six chamberings: 32-20, 38-40, 44-40, 38 Special, 357 Magnum or 45 Colt; a total of 36 variations.  Operation First Generation Single Action Army from 1918, 32 WCF (32-20)
The Single Action Army action is a refinement of the earlier Colt percussion revolvers and the Colt 1871 cartridge revolver. The cylinder is mounted on a central axis and operated by a hand with a double finger whose more extended action allowed the cylinder-ratchet to be cut in a larger circle, giving more torsional force to the cylinder. Three notches on the face of the hammer engage the sear portion of the trigger, affording four basic hammer positions. The hammer when fully lowered rests within the frame. Drawn slightly to the rear, the hammer engages the safety notch of the sear and holds the firing pin out of direct contact with a chambered cartridge. Like the earlier percussion revolvers, the Single Action Army was designed to allow loading of all of the chambers. The safety notch replaced pins on the rear of the percussion revolver cylinders which served the same purpose as the safety position by preventing hammer contact with the primer/percussion cap. At some point in the history of the Single Action Army, many users adopted the practice of leaving an empty chamber under the hammer because a sharp blow could damage the mechanism and allow the fully loaded revolver to fire. This practice is now universally recommended. Drawn back about half way, the hammer engages the second notch. This cams the cylinder bolt out of engagement and allows the cylinder to rotate for loading. Fully cocked, the revolver is ready to fire. Cartridge ejection is via the spring-loaded rod housed in a tube on the right side of the barrel. The loading sequence: 1. Place the revolver on half-cock and open the loading gate to the side (photo 6); 2. Load each chamber in sequence (original), setting the hammer in the safety notch when finished; or (safe and prudent method) load one chamber, skip the next, load the remaining four chambers, close the loading gate, draw the hammer to full cock and lower fully, making sure that the firing pin is over the empty chamber. 3. Firing the revolver is accomplished by drawing the hammer to full cock and pulling the trigger. The hammer must be manually cocked for each shot.
It is possible to fire the SAA rapidly by holding down the trigger and "fanning" the hammer with the other hand. While this is often shown in movies, it is inaccurate and unsafe and should not be attempted; it also can damage the revolver mechanism and cylinder, requiring expensive replacement. Photos 3 7 show a U.S. Fire Arms Mfg. Co. revolver. The U.S. Fire Arms Safety and Instructional Manual for Single Action Firearms describes safe handling procedures and user responsibility.  U.S. Inspector's Marks Colt Single Action Army, serial No 5773 7th Cavalry issued
All original, good condition, first generation Single Action Armies (those produced between 1873 and 1941) are among the most valuable to the collector. Especially valuable, often going for well over $10,000, are the OWA (Orville Wood Ainsworth) and the Henry Nettleton inspected Single Action Army Colts. The very first production Single Action Army, thought lost for many years after its production, was found in a barn in Nashua, New Hampshire in the early 1900s. The OWA Colt refers to the earliest issued Single Action Army guns which were inspected by Orville W. Ainsworth. Ainsworth was the ordnance sub-inspector at the Colt factory for the first 13 months (Oct. 1873 to Nov. 1874) of the Single Action Army's production. It was Ainsworth who inspected the Colts used by Col. G.A. Custer's 7th Cavalry at the Battle of the Little Bighorn. The number range of possible Little Bighorn Colts is 4500 - 7527.
Henry Nettleton was the ordnance inspector in 1878 at the Springfield Armory. Second only to the OWA Colts, Nettleton Colts are prized by serious collectors. Both the Nettleton and OWA Colts have the cartouche (OWA or HN) on the left side of the wood grip.
The largest group of [link] Cavalry revolvers was inspected by David F. Clark, his DFC cartouche will be encountered on revolvers inspected from 1880 to 1887.
Another historical military SAA revolver is the Artillery Model. It was issued to the rear-echelon troops, artillerymen, and such during the Spanish-American war period. Following the Indian wars, in 1895, the 7-1/2" cavalry SAAs had fallen into disrepair and had been sent back to the Colt factory or Springfield Armory to be refurbished, fitted with a shortened barrel (cut from a 7 1/2" (191 mm) to a 5 1/2" (140 mm) and re-issued. Most of the Artillery Colts had mixed numbers. The standard military revolver at the time was the Colt double-action New Army revolver, chambered in 38 Colt. Theodore Roosevelt's Rough Riders charged up San Juan Hill wielding the Artillery Model. Artillery models usually can be identified by the original inspector's cartouche (such as OWA or HN) on the left side of the grips and the cartouche of Rinaldo A. Carr (RAC), the inspector who inspected the refurbished guns, on the right side.  The Bisley Model Colt Bisley Model .38-40 WCF, shipped 1904 to Copper Queen Cons. Mining Co. Bisbee Territory of Arizona
The Colt Bisley was introduced in 1894 as a target pistol, the name Bisley came from the famous firing range in Bisley, England. It can be distinguished in the longer grip, the wider hammer spur and the wide trigger. The distinguishing feature of both of the Target Models is the top strap, which is flat and fitted with a sliding rear sight adjustable for windage only. The front sight is a removable blade, which fits in the slotted base attached on the barrel. The revolvers were supplied with different blades for elevation.
The Bisley mainspring is longer than the SAA mainspring and is not interchangeable with it; it is attached to the hammer with a stirrup and has a forked upper end to connect it to the stirrup. The serial numbers are stamped on the frame, the back strap and the trigger guard strap; at the end of the production with tiny dies.
Bisleys were serial numbered in the range of 156300-331916, in the same sequence as the Single Action Army. All Bisleys after No. 161,000 had "BISLEY MODEL" with the caliber stamped on the left side of the barrel, which is rare for older Colt revolvers. The most common calibers were the .32-20, the .38-40, the .45 Colt, the .44-40 and the .41 Colt. A total number of 44,350 were manufactured. The production of the Bisley was terminated in 1912, but the serial No. 331916 was shipped after the 1st World War. Most Bisley Standard Model Revolvers were shipped to a U.S.A. address, not for target shooting but for self-defense because the grip and hammer were ideal for fast shooting.  Engraved Single Actions
Often even more valuable are original factory-engraved Colt SAA's. Colt engraved less than one (1) percent of 1st-generation production, which makes them extremely rare. Engraved pieces often were ordered by or for famous people of the day, including law/police, government/heads of state. Colt employed a number of highly skilled engravers, many of whom were highly-trained artisans who immigrated to America from Europe.  Legacy Second Generation Colt engraved in 19th Century pattern
The power, accuracy and handling qualities of the Single Action Army made it a popular sidearm from its inception and well into the 20th century. Such notable old west personalities as Wyatt Earp and William Barclay 'Bat' Masterson favored these revolvers with Earp's elusive and possibly apocryphal "Buntline Special" Colt Buntline gaining fame in the Earp Biography by Stewart Lake. An order for a somewhat customized Single Action Army from Masterson remains in the Colt archives. The association with the history of the American West remains to the present century and the revolvers remain popular with shooters and collectors. Famed British adventurer and soldier T. E. Lawrence ("of Arabia") had a special fondness for this weapon because it saved his life during one of his pre-World War I trips to Mesopotamia; he was attacked by an Arab bandit who stole the gun and tried to shoot Lawrence. However, the bandit was unable to fire the weapon because he did not understand the revolver's single-action mechanism. Lawrence thereafter always carried one of these weapons for good luck. (see Lowell Thomas, With Lawrence In Arabia (1924)). US Army General George S. Patton, who began his career in the horse-cavalry, carried a custom-made SAA with ivory grips engraved with his initials and an eagle, which became his trademark. He used it during the Mexican Punitive Expedition of 1916 to kill two of Pancho Villa's lieutenants, and carried it until his death in 1945 shortly after the end of World War II.
In the early and mid-20th century, original Peacemakers lacking historical provenance and not in pristine condition were not particularly valuable. They served as raw material for early enthusiasts such as Elmer Keith, Harold Croft and R. F. Sedgley who modified the revolvers to enhance performance and experimented with more effective ammunition. At the beginning of the 21st Century, first and second generation SAA's are highly regarded as collectors' items and often considered too valuable to shoot.
After the 2nd World War, new interest in the SAA started and firearms enthusiast William R. Wilson recognized the need and the opportunity. In 1953 Wilson founded the Great Western Arms Company to produce an almost-exact clone of the old Colt SAA for television and movie westerns. The Great Western revolvers were 100% manufactured in Los Angeles.
Later Colt editions are more common, and various copies and near-copies of the revolver are made by A. Uberti of Italy, now owned by the P. Beretta firm, and others. American manufacturers include Colt Manufacturing Company, which still retains the model in its catalog. U.S. Fire Arms Mfg. Co. builds several variations that are true to the original first and second generation specifications. STI International has introduced a very precisely made Single Action Army with a modified hand/spring assembly designed to last longer than the originals.
The Single Action Army is the precursor and inspiration for modern sporting revolvers from Ruger, John Linebaugh, Freedom Arms and others.