Today I want to talk about the quintessential American handgun cartridge, the 45 ACP. Be warned, however, that no discussion of this cartridge would be complete without exploring the origins of US military obsession with the Lord's Caliber. So if you're just looking for someone to agree with your opinions, validate your decisions, or enable your addiction; this might not be your video, there are some inconvenient truths and unpopular opinions ahead.. However, if you're ready for a deep dive into cartridge development, stick with me, I promise we'll get there but it's going to be a long story. That said, let's go all the way to the beginning and look at the facts and events that led us into the modern era with the Year of Our Lord Browning 1911. And remember, if you think I'm wrong: fight me in the comments; if you can prove I'm wrong: shoot me an email, I'd love to hear from you.

This story begins with Samuel Walker, Captain in the Texas Rangers. The Rangers, fighting Indians and Mexicans in the southwest, had been among the earliest units to adopt the Colt Paterson revolver and the men perfected its use on horseback, a decided advantage over dismounting to fire and reload as was typical of other mounted soldiers using single-shot pistols and carbines. In 1846 Walker was appointed Captain in the United States Army and authorized to raise a volunteer company of mounted rifleman. Walker traveled to Washington D. C. to recruit, train, and equip his new command. In that interest he met with Samuel Colt to request a new type of revolver. The proposed gun was to be 6-shot, carried on a saddle, capable of being used one-handed from horseback, should fire 50-Bore conical bullets, and be powerful enough to equal the currently used carbines to a range of 200 yards. The resulting 1847 Colt-Walker pistol was a massive 4.5lb revolver firing 148gr conical bullets over a 60gr charge of black powder, with a velocity just over 1100fps out of a .44 caliber 9in barrel.

To clarify, the inner diameter of a barrel is called the bore. A numbered bore size, also called gauge, expresses the number of round lead balls of that diameter that it takes to make up 1 pound. Dividing 1 pound of lead into 50 round balls results in a diameter of .453 inches weighing 140gr each. During the 1800s it became more common to describe bore size by caliber. Caliber is the same measurement expressed in inches. Prior to the 1870s barrel sizes were named based on their smallest inner diameter, before the rifling grooves were cut. For efficiency and accuracy lead bullets should have the same outer diameter as the rifling grooves of the barrel. Since the 1700s rifling grooves have typically been cut about .007 inch deep. So, a barrel with a groove diameter of .453 inches will have an inner diameter of approximately .44 inches.

To make this even more complicated, original muzzle loading revolvers typically used a groove diameter slightly larger than the bullet in order mitigate the effects of black powder fouling. However, chambers were slightly smaller than the bullet diameter to ensure a tight seal when seated over the powder charge. For the Colt-Walker this meant a .453 inch bullet was forced into a .451-.452 inch chamber before being fired through a barrel with a .453-.454 inch groove diameter. If you just don't think about it, it makes perfect sense.

It was Captain Walker's specification of bullet size that would start six generations, and counting, of US military obsession with the 45 caliber pistol.

The Colt-Walker was a bit too ambitious, however. It proved difficult to handle and due to the large powder capacity and inexperience of the men using it, at least one quarter of issued pistols experienced burst cylinders or barrels within the first year. This led to the pistol being used with a charge of powder closer to 45gr than the 60gr originally intended, with an average velocity around 900fps.

In November of 1847 additional pistols were ordered with requests to shorten the cylinder and barrel. The resulting 1848 model, later known as the Colt Dragoon, was reduced in weight by only 4 ounces and reportedly had a 50gr capacity which yielded a velocity of 1000fps with the same 148gr conical bullets out of the now 7.5in barrel. In practice, the new model was typically only loaded with 30-40grs of powder resulting in an average velocity between 750-850fps. These pistols were again fielded by United States Mounted Rifleman, this time in the Northwest Oregon Territory during the Gold Rush. The new pistols were easier to handle and less prone to misuse, giving them a very favorable reputation.

During the 1850s the US military expanded its armament and sought to keep pace with technological advancements. In pistols, the use of paper cartridges became common and bullets with a grease groove were favored. In 1855 the US Army adopted the 36 caliber Colt 1851 revolver. However, the Mounted Rifleman and Dragoons continued to use their preferred .44 caliber pistols, with requests to Colt for an updated version. With their patents expiring, Colt looked for possible innovations, which were found with Company Superintendent Elisha Root. To meet the Ordnance request in the most cost efficient way, Colt combined features of Root's patent with the model 1851 frame and an enlarged cylinder and barrel. The resulting pistol had quite a bit of contouring to ensure a light weight, giving the Model 1860 a much more elegant appearance and a over a pound less weight than the 1848 Dragoon.

Despite the innovation and demand, Model 1860 revolvers were not ordered from Colt until the wave of secession in April and May of 1861 during the outbreak of the American Civil War. The new model maintained use of the same .453 inch bullets and was optimized for paper cartridges. With a charge of 30gr black powder average velocity out of the Army standard 8 inch barrel was around 850fps. 

Back in 1856, when Colt's patent for a revolving cylinder expired, the Smith and Wesson company took advantage of a patent Colt had overlooked and designed the first US revolver to fire metallic cartridges. Smith and Wesson's small rimfire revolvers proved to be popular backup weapons during the Civil War, establishing the company as a competitive rival to Colt, though lacking a large caliber pistol. During 1869, Smith and Wesson developed their own .44 caliber revolver, and in 1870 released the Smith and Wesson Model No.3, which may have been the most advanced handgun of its time. The only shortcoming of the pistol, from the military's viewpoint, was its use of a rimfire cartridge, the 44 Henry, with a case and bullet .441 inch in diameter. The Ordnance Department would order 1000 No.3 pistols in December of 1870 but insisted on a centerfire cartridge. Smith and Wesson responded by simply adapting the 44 Henry to use a centerfire primer and called the new cartridge the .44 American. It fired a 200gr bullet just under 700fps. While the Army liked the advanced features of the gun, they found it be too complex and delicate while in service use. 

As a side-note, the No.3 revolver was also presented to the Russian military, who likewise requested changes to the cartridge. The resulting .44 Russian used the same case as the .44 American but employed a bullet with a consistent .432 inch diameter. This would be the progenitor of modern .44 caliber cartridges.

When the Rollin White patent, controlled by Smith and Wesson, expired in 1871 Colt designed their own cylinder conversion to chamber a new cartridge in their existing revolvers, the 44 Colt. The case and bullet were .451 inch in diameter, with a case length of approximately 1.12 inch which held a 21-28gr charge of black powder. It typically fired a 210gr bullet with a velocity around 700fps. The conversion was applied to existing US Army revolvers as well as new pistols produced at Colt's to use up available parts.

At the same time, Colt designed a new pistol specifically for breech loading cartridges, but still based on the conversion patents. The resulting Model continued the open-top construction with a larger frame and cylinder. Rather than firing the new 44 Colt, the 1872 pistol was chambered for the widely available 44 Henry rimfire, and released for commercial sale as well as being submitted for military trials.

Throughout 1872 the Army Ordnance Board conducted trials with all category of small arms to determine what equipment would be suitable to meet their future needs and replace outdated equipment. Even at the time, the board faced accusations of rampant corruption and back-dealings. The  44 Russian was a solid front-runner for pistol cartridges until the report of carbine tests concluded that all small arms should be standardized at .45 caliber. Colt was favored for pistol manufacture, but the 1872 model was dismissed for lack of a solid frame and request for a more powerful cartridge. Continued development resulted in the Colt Model P, which was adopted by the Army in 1873 and would come to be universally known as the Single Action Army. A new cartridge was developed alongside the pistol and called the 45 Colt, or more commonly 45 Long Colt. The cartridge case was 1.285 inch long and fired a 255gr .452-.454 inch inside lubricated bullet with a 40gr charge of black powder for a velocity of 850fps.

In 1875 Smith and Wesson produced an updated No3 revolver incorporating advancements patented by Calvary officer Major George Schofield, brother of then Major General John Schofield ex officio President of the Ordnance Board. Contrary to later rumors of favoritism, General Schofield was serving in Hawaii and does not appear to have been directly involved with decisions on weapon selection at the time. It was requested that the new pistol chamber the 45 Colt cartridge, but Smith and Wesson instead produced a new .45 cartridge with a 1.1 inch long case, firing a 230gr .454 inch inside lubricated bullet at a velocity of 730fps. Just over 8,200 pistols were purchased between 1875 and 1879.

In 1879 cartridge manufacturing came within sight of the modern era with the development and combination of solid head cases and boxer primers. Prior to this, internally primed or balloon-head cases were standard. The Ordnance Board applied the developments to the 45 Smith and Wesson,  designated as Reloading Cartridges, allowing cases to be reloaded in the field. Combined with the ability for use in both Smith and Wesson and Colt revolvers, the new reloading cartridges reduced costs and reliance on factory logistics. Continued and extensive testing would produce the Model 1882 Ball Cartridge for Caliber .45 Revolver.

The Model 1882 Cartridge, also designated 45 Colt Government, was originally identical to the 45 Reloading Cartridge, with a 230gr bullet and 28gr charge of black powder. In 1877 it was updated to use the smaller rim diameter of the 45 Long Colt. In 1890 case material was changed from copper to tinned brass due to being lower in cost and stronger. 

Between 1886 and 1892 trials were conducted which led to the adoption the swing-out cylinder Colt double-action revolver and its 38 caliber cartridge firing a 148gr bullet at 750fps, which admittedly sounds rather anemic until you remember that it is equivalent to the lower end of loads used in the Colt Dragoon.  The revolver was first  adopted by the Navy in 1889, and after additional development the Model 1892 was accepted for all branches of the Army, a matter of some resentment among cavalry officers who favored the tradition and cartridge of the .45. Ironically Cavalry soldiers were the first to be issued the M1892, with .45 caliber pistols being recalled from all units except horse artillery starting in 1893. The horse Artillery complained about the length and weight of the .45s, so the Ordnance Department began shortening the barrel to 5.5 inches during refurbishment. Pistols not issued to artillery units were put into storage. It was, however, justifiably despised for its heavy trigger pull, 13lbs single action and over 18lbs in double action compared to 4-6lbs of earlier Colt's used. This was a safety feature which senior military found not only desirable, but essential. While the M1892 was more complex and difficult to repair in the field, it served favorably throughout conflicts in the Caribbean, South America, Asia, and against the Spanish in the Philippines. The indigenous Filipinos, however, was a unique situation. 

The occupying force in the Philippines, if oversimplified, consisted of a military police called the Philippine Constabulary which was indigenous locally and overseen by a mix of indigenous and U.S. Officers regionally who were, in turn, overseen by a U.S. Military General, with the title of Governor. The Constabulary were tasked with maintaining peace and order, while the U.S. Military primarily acted to subdue combatant forces in open rebellion, as well as building infrastructure. Due to the mixed and transient loyalties of the indigenous population under U.S. command, arms distributed among the Constabulary were typically limited to M1892 revolvers and outdated single-shot Springfield carbines and Remington shotguns. The intent was to prevent supplies being used against US forces and ready identification of misappropriated armament. The mix of Army, Navy, and Cavalry units stationed in the Philippines were typically armed with the M1892 revolver and the Krag-Jorgensen  rifle or carbine.

Back in the US, in 1898 the remaining Schofield revolvers were sold as surplus to the commercial market. By the end of the year 650,000 45 Long Colt cartridges were purchased for use in the Philippines, however, the order was set aside for proof testing refurbished Colt revolvers as it was prone to split cases and blown primers. It is unknown why this order was placed, as there does not appear to have been any troops with issued 45 caliber pistols in the Pacific at that time. 

With the outbreak of hostilities in late 1899 and Filipino adoption of gorilla-style tactics reports began decrying the performance of the .38 Colt revolvers and 30-40 rifles when used in close combat. The Civil War era volley-fire tactics that had been successful against the Plains Indians and conventional  armies were simply not effective in the cities and jungles of the Philippines and led to a high number of causalities.  In response Smith and Wesson developed the 38 Special cartridge, firing a 158gr bullet at 850fps, which could also be used in the Colt revolver, and more Winchester and Remington shotguns were procured. Additionally, cavalry requests for their .45s finally had a reasonable justification.

In 1901 the .45 M1882 Cartridge was updated further, no longer tinning cases and using a 225gr bullet and 26gr of black powder. 2 million cartridges were produced and sent to the Philippines, along with the first order of refurbished M1873 pistols. By the time this equipment arrived, however, the majority of fighting had subsided. A provisional government was established and  rebel forces had retreated to the Moro populated southern islands. Intermittent fighting with the Moro would continue until 1914.

In 1902 an updated version of the Colt M1878 revolver was sent for use by the Philippine Constabulary. The Colt 1878 had problems with light primer strikes using the M1882 ammunition, to address this Colt increased strength of the hammer spring, resulting in an egregiously heavy trigger, which was in turn address by making the trigger large enough to pull with two fingers. Even the 1902 abomination couldn't fix the Colt's difficulties setting off military ammunition, and in 1903 special primers were designed to update the M1882 cartridge. Still, the Philippine Constabulary found the pistol unusable and most sat in store rooms without ever leaving their shipping containers. 

It is a seldom admitted fact that use of .45 caliber revolvers had little, if any, effect during fighting in the Philippines. They proved to be no more effective at stopping or killing determined attackers than the standard issue Colt 38. The Constabulary adapted to using a minimum of 2-man patrols, where one was armed with a Krag carbine and the other a Winchester 1897 shotgun. The Army, likewise, adopted the liberal use of 12ga buckshot during jungle fighting and close range engagements. Cooperation of the local population after the elimination of piracy by coordinated Army and Navy units was undoubtedly the largest single stabilizing factor during the Philippine conflict.

It is at this point that .45 automatic cartridge began development and branches off from that of the revolver. The military's .45 revolver cartridges would not use jacketed bullets until 1905 and did not switch to smokeless powder until 1908.

While the Philippine conflict was ongoing, Colt and the illustrious John Browning were hard at work developing an automatic pistol for the military. The Colt Model 1900 and 1902 Military both saw service in the Caribbean and Philippines, during field trials with the Cavalry. While they admitted it's greater accuracy and reduced maintenance compared to the M1892 revolvers, they were quick to bemoan that the caliber was just as small as the revolver. At the same time, between 1901 and 1903, Colt had also been working to develop a .41 caliber cartridge for use in the automatic pistol, without much success.

In October of 1903 the US Ordnance Department tasked a two-man board to address the insufficient stopping power and shock effect of the Colt 38 revolver cartridge, by conducting tests to determine what design and caliber of bullet possessed those essential qualities. While many cite the tests as definitive evidence of cartridge superiority, it was largely a farce. The concepts of stopping power and shock effect are almost as poorly defined or understood today as they were in 1900. For the purposes of the tests conducted by Captain John Thompson, officer in the Ordnance Department, and Major Louis LaGarde, surgeon and former Cavalry Officer during the Indian Wars, Stopping Power was defined as the ability of a bullet to fracture and cause splintering of long bones in the arms and legs. This was tested by shooting human cadavers and butchered horse legs, and observed by x-ray. Shock Effect was not defined at all, but was assumed to be inferred by the measurable effects of energy transfer when a bullet passed through a cadaver, as well as the visual distress of live cows when shot through the lungs or intestine. Observation of shock effect was done by hanging a cadaver and measuring how far backward different parts traveled when shot, and with live cattle by determining how many shots were required before the animal fell from its feet and recording the time from the first shot until the animal died, which was anywhere from 3 to 9 minutes for all cartridges tested. Tests with cadavers were likely completed by late November, and tests with cattle were done the following March in 1904. Nine cartridges were used, 30 Luger, 9mm Luger, 38 Colt, 130gr fmj 38 ACP, 120gr soft point 38 ACP, 45 Colt, 45 Colt hollow-point, .455 Webley with a hollow-point hollow-base wadcutter, and .475 Eley. The tests on cadavers, while common at that time, have been called into question with modern medicine as lacking correlation to the theory being tested or to the results inferred. And cattle testing was clearly biased, ignoring results that did not confirm the conclusions made. Findings were contradictory, claiming that the same cartridge which lacked the penetration to kill a cow when shot in the head three time nonetheless possessed the greatest stopping power, and that rapidly expanding bullets were the most effective type but should not be used for risk of violating the 1899 Geneva Convention. They further outlined specifications for a jacketed bullet construction that not only had not been tested, but didn't exist with any commercial manufacturer. The only reasonably scientific recommendation was that soldiers who are to be armed with a pistol should be taught basic human anatomy and relentlessly drilled in proper shot placement, due to the -quote- large amount of the target area of the human body which offers no hope of stopping an adversary...when hit. Let me say that again a little slower, I know a lot of people don't want to hear it, the Thompson-LaGarde tests found that any pistol cartridge, from .30 to .475 caliber, was potentially incapable of stopping a man unless shot in a vital area, namely the heart, spine, or brain.

Before the cattle tests had even been done, Colt was informed the Ordnance Board would be recommending a .45 caliber cartridge, likely by Thompson himself. Colt abandoned the .41 Auto and began reworking the project. In February 1904 cartridge specifications were sent to UMC for the development of production samples, while Colt's worked on refining the pistol design.
In March 1904 Frankford Arsenal was likewise ordered to start development of a 45 automatic pistol cartridge, which, after a year of work, were completely unusable.

In September 1904 Colt sent Browning two 1902 pistols to be reworked for the 45 cartridge. The new designs were patented, resulting in a scaled up version of the m1902 with an improved locking system that would quickly become the Colt Model 1905.

During March and April of 1905 samples were sent between Colt, Browning, and UMC for a rimless .45 caliber cartridge with the same case and overall length as the 38 ACP, using a jacketed 200gr bullet and 5.5gr Bullseye powder, cannelure on the case with no crimp at the case mouth. After reducing the powder charge to 5.1gr, for a velocity around 900fps, the samples were approved and 1 million were ordered for testing with Colt. 
In June a prototype pistol was sent from Colt to the Ordnance Department for testing their cartridge samples. In September another pistol was sent to the Ordnance Department, this time a production sample.

In November another 1 million cartridges were order from UMC for Colt, and by December the first commercially sold Model 1905 pistols were being shipped for distribution.

In late 1905 Frankford Arsenal was notified they would be required to provide ammunition for upcoming trials to select an automatic pistol. During 1906 cartridges were designed with both rimless and semi-rimmed cases, .923” long firing a 230gr bullet 800fps. Tests were scheduled to begin September 1906, but the poor quality of Frankford's ammunition, and their inability to manufacture it, delayed testing until January 1907. By June they simply began ordering ammunition from UMC, specifying a 230gr bullet and 800fps velocity, all other aspects being the same as UMC commercial cartridges.

During 1906 UMC made adjustments to the extractor groove, rim thickness, and primer.

Testing throughout 1907 resulted in a number of changes being requested to the pistols still in trials and an order for 200 production samples for field testing. Colt shipped the 200 gun order of what is known as the Colt Model 1907 in March of 1908. The pistols were divided up and sent to different militrary units throughout the United States and the Philippines. Reports came back quickly with soldiers noting excessive recoil, poor grip, jams, and frequent parts failure.

Again, the Ordnance Department contracted with Winchester and UMC for cartridge production, specifying a 230gr bullet .452 inch in diameter. Winchester ammunition was made without a cannelure on the case, but after experiencing issues with bullet setback it was required once again.

By December 1908 the Pistol Trials Board concluded that neither the automatic pistol nor the average soldier was ready for it's general use. While further testing of automatics was scheduled the Ordnance Department ordered 6000 Colt New Service revolvers chambered in 45 Long Colt.

Nearly all of the M1907 pistols were recalled and further improved by June 1909. Again reports came back quickly noting excessive recoil and parts failures. Even while pistols were being recalled however, Colt's again turned to John Browning, who redesigned the pistol. The new prototype would be known as the Model 1909, and tests were scheduled for August. Further tests were recommended and 24 Pistols were made and sent to various military branches throughout the country. Tests were completed by April 1910. While further improvements were recommended, the Cavalry, which was the only unit who's pistols had not experienced any failures, did not recommend the pistol for adoption. Officers still felt their men were not safe enough to use an automatic pistol. 

To make the timeline somewhat confusing, before the M1909 pistols even shipped out, Colt and Browning were making improvements and the new pistol was tested in February 1910. The 9 pistols made are now referred to as the Colt Model 1910. Testing continued until November, in which the pistol experienced several cracked frames and one cracked barrel.

An additional 9 pistols were made with changes to address the frame and barrel issues as well as adding a manual safety specifically for the cavalry. On March 11, 1911 the new pistols were subjected to a now infamous 6000rd endurance test without a single failure. On March 19 the US Military officially adopted the Automatic Pistol, Caliber .45, Model of 1911. 

With the pistol finally selected the Ordnance Department tested, standardized and adopted its cartridge, the Cal. .45 Automatic Pistol Ball Cartridge, Model of 1911. A change was made to the primer, which was shorter than that used in the rifle to avoid misidentification. A slightly tapered 230gr fully jacketed bullet, .450-.451 inch in diameter was specified with a velocity of 800fps. The new cartridge would be produced by Frankford Arsenal. Two powders were approved, DuPont Pistol Powder No.2, which was Bullseye powder, and Pistol Powder No.3, another DuPont powder that appears to have been discontinued sometime the 1930s or 40s. As a side note, current Bullseye powder made by Alliant is rumored to use the same formula originally developed by Laflin and Rand in 1898. Laflin and Rand was acquired by DuPont around 1902, which was broken up under anti-trust laws in 1912, forming Hercules Powder, which was then purchased by Alliant in 1994.

And thus, in the Year of Our Lord Browning 1911, we arrived in the modern era of pistol design.

Between 1911 and 1918 experiments were made to use rejected 30-06 cases to load 45acp, however this practice was never implemented due to the extreme pressure created by using the reduced capacity cases..

From 1912 to 1914 an increasing number of commercial manufactures were contracted to produce the military cartridge to meet the extreme demands of WWI. 

In 1917 the Colt New Service Revolver was modified to chamber the .45 Auto cartridge with half-moon clips. The M1911 cartridge was updated to include three dimples crimped at the case mouth to prevent the bullet from traveling forward under recoil when used in the revolvers.

During 1925 the M1911 cartridge was updated again, no longer using a tapered bullet, with a .450-.4515 inch  in diameter. 

In 1926 bullet jackets were no longer tinned, and red shellac was used to waterproof the case mouth and primer pocket.

In 1932 bullet diameter was again increased slightly to .4505-.4515 inch. Also, Frankford Arsenal discontinued using Bullseye powder, as the high nitroglycerin content was found to be desensitizing the TNT used in their primers. 

It wasn't until 1935 that Frankford Arsenal added machines to check case powder levels in their production assembly, due to batches that went out with double and triple powder charges. In response, DuPont developed Pistol Powder No.5 which would more fully fill the case with a 5gr powder charge, and it became the standard powder used by Frankford Arsenal until discontinued in 1940. It is speculated that after 1940 Bullseye powder was again used with a different primer formula, but this has not been confirmed. 

From there, the rest is history. Since WWII nearly every conceivable specialty variation has been tried and tested, with the US military until their adoption of 9mm in 1985 and even more so on the commercial market. Use of higher pressure +p cartridges comes and goes in vogue, but the 230gr bullet with a velocity of 800-855fps is still the standard, and was used by the US Marines until 2022.