Comparing handgun cartridges on the basis of power can help shed light on the terminal efficacy of various calibers across history, and to what degree modern caliber choices are important. For this comparison, I'll be sorting calibers by range of foot pounds energy (fpe). When categorizing, I estimated fpe assuming the most common commercially available power range for cartridges that are commonly loaded by people who actually carry or carried that weapon, so these estimates are necessarily speculative on that basis, though still informative when deciding between and among caliber choices. I am also assuming the most common handgun barrel length for each caliber that is commonly carried. I also ordered the calibers by date of historical introduction when possible.
0-100 fpe: This power range constitutes the lowest acceptable output of a handgun. The weapons listed show that this range of power would have been historically considered submarginal by most. The bow is an exception, but requires a sharpened arrow to deliver terminally effective wounds. Bullets at this low speed are unlikely to be effective against bone and are more prone to deflection. Many of the firearms carried in these calibers are carried by individuals who would prefer a handgun for self defense, but either were not able to historically or legally carry more powerful alternatives, or prefer to carry a weapon of very small size and are unconcerned about the limitations of these rounds.
60 pound hunting recurve bow
black powder .31 caliber pocket revolver
.22 lr pocket pistol
.32 S&W long
.25 acp
.22 magnum (snubnose)
100-200 fpe: This power range constitutes the standard expected lethality of a handgun from 1850-1860, which spans much of the American frontier period and American Civil War. The Colt 1851 Navy was carried across the American west by lawmen and rangers and was widely regarded as effective against human combatants. As cartridge technology evolved, the .38 short/long cartridges approximated this power range. Interestingly, these early .38 revolvers were later seen to be famously inadequate in the Philippine insurrection against drugged Moro warriors. Another analog, the .32 auto was later popular from the early 1900's into the 1950's, most commonly by civilians and military officers who did not expect direct armed conflict. This power range is likely effective against unmotivated attackers as a tool of persuasion or psychological fear, but is not to be relied on for warfare or against highly motivated attackers.
black powder .36 1851 Colt Navy revolver (round ball)
.38 short/long
.38 special (snubnose)
.32 acp
200-300 fpe: This power range constitutes the standard expected lethality of a handgun after initial development of smokeless powders, improved conical projectiles, and/or improved metallurgy in the late 1800's. The 1860 Army was a revolver that became possible only after Colt improved handgun materials to the point that larger powder charges could be safely fired in a relatively compact frame. It should be noted that this range of power was deemed acceptable for use against enemy horses in war and against black bear in the 1850's. In conjunction with this innovation, the use of heavier conical bullets expanded the capabilities of the 1851 Navy revolvers currently in service. Later, the development of metallic cartridges ushered in the use of larger diameter revolvers like the .45 Schofield, which could reload faster than the Colt system, and .44-40, which could be chambered in both revolvers and lever action carbines. This power range was retained as the standard expectation of handgun lethality until nearly the 1980's following the widespread adoption of the .38 special (4 inch barrel) as the standard American police arm. One reason for the use of heavy recoiling .357 cartridges in a snubnose revolver could be to approximate the power of larger revolvers in a smaller frame. At the same time, in semi-automatic handguns, the .380 auto cartridge was popular with civilians and military officers as a concealable backup arm that allowed more power than the .32 acp, while still allowing for safe operation in a straight blow-back action and comparable power to the ubiquitous full size .38 specials. Some prefer the .32 H&R magnum over the .38 special since the smaller diameter allows 6 shots to fit in a concealable J-frame sized revolver that would typically only hold 5 rounds of .38 special. Another contemporary niche could be individuals who dislike the recoil of .357 in a snubnose platform and prefer the .44 special snubnose for its comparable power with less recoil.
black powder .36 1851 Navy (with conical projectiles or large powder charge round ball)
black powder .44 1860 Colt Army (round ball)
.45 Schofield
7.62 Nagant revolver
.38 special standard pressure (4 inch barrel)
.380 acp
.44 special (2 inch barrel)
.357 magnum (2 inch barrel)
.32 H&R Magnum
300-400 fpe: This power range constitutes the standard expected lethality of semi-automatic handguns following the advent of designs that allow higher pressured rounds to safely cycle. Locked breech operating systems allowed for semi-automatic pistols to safely cycle ammunition of high enough pressures that they could not be safely fired in straight blow-back handguns. This was accomplished with the advent of mechanisms to delay the opening of the firing chamber until pressure had reduced. The first cartridges of this kind were most common in military applications. 9 mm and .45 acp cartridges were developed for use with locked breech designs in the early 1900's and were deemed adequate for use in war against human combatants. In revolvers, this power range was achieved first by the development of the 1858 Remington revolver, which allowed a greater powder charge than the Colt pistols due to its enclosed frame. Later, the merely adequate performance of the .38 special prompted the development of +p+ loadings, which occupied an intermediate power range between standard pressure and .357 magnum pressure and is still a preferred power range among revolver users today. The ubiquitous modern 9 mm pocket pistols with 3" barrels and modern +p ammunition also occupy this power range, which is widely regarded as adequate for self defense against human combatants.
black powder .44 1858 Remington Army (round ball)
black powder .44 1860 Colt Army (conical)
9mm historical standard pressure/modern pocket pistol with +p ammunition
.44 special (4 inch barrel)
.45 acp standard pressure circa 1940's
.38 sp +p+ Buffalo Bore load (2 inch barrel)
400-500 fpe: In the black powder era, this power range would have only been achievable with large caliber muzzle loading pistols like the Howdah hunting backup pistols and Flintlock pistols in military service loaded with conical bullets, or with extended barrels. The 1847 Colt Walker was the most powerful of these black powder examples and was the most powerful repeating handgun in existence until the development of the .357 magnum. It achieved this power range with a 9" barrel and a massive frame carried exclusively by mounted cavalry for intended use against enemy horses or marauding bears. After the advent of cartridge technology, the .45 Long Colt surpassed the power of most other black powder handgun rounds of its time. Its competitor, the .44-40 cartridge which won the West had somewhat less power, but could be loaded in both revolvers and carbines, which gave it an advantage in versatility. In modern revolvers, this power range includes mild .357 magnum cartridges, which can also be loaded in carbines for comparable versatility. In modern handguns, this power range was first realized by the .40 S&W after the 9 mm standard pressure was deemed inadequate against motivated attackers armed with high powered rifles in the 1986 Miami shoot out. First the 10 mm was developed, but excessive recoil of the round prompted a reduction to the .40 S&W, which was accepted through the 80's and 90's in American police departments. Modern ammunition manufacturers also continued to expand their offerings to include modern +p loadings of 9 mm and .45 acp that now rival .40 S&W performance in full size handguns. This power range is considered more than adequate for self defense against human combatants and used to be considered adequate for hunting fleeing large animals from horseback as well (before more powerful alternatives became available).
black powder .50 caliber musket pistol (w/conical bullet)
black powder .44 Colt Walker 1847
.45 Long Colt
.44-40 revolver
.357 magnum (3 inch barrel)
.40 S&W
.45 acp +p
9 mm +p full size
.327 magnum (3 inch barrel)
.38 sp +p+ Buffalo Bore load (3-4 inch barrel)
500-600 fpe: This power range was initially adopted for use against early body armor worn by mobsters in 1930's USA and against automobile engine blocks. The development of the .357 magnum by Elmer Keith and ammunition manufacturers allowed for the creation of the most powerful handgun cartridge until the creation of the .44 magnum in the 1950's. This power range is widely considered devastating against human combatants. This power range also enabled the first ethical hunting of medium sized game with handguns. In the modern day, the .357 SIG, .40 S&W +p, and .45 acp +p are the modern examples of this power range in full size semi-automatic handguns. In 2007, the introduction of the .327 magnum allowed for this energy range with potential for higher capacity in full size revolvers.
.357 magnum (4 inch barrel)
.40 S&W +p
.45 acp +p
.50 GI
.357 SIG (full size)
.327 magnum (4 inch barrel)
600-800 fpe: This energy range encompasses higher end handgun hunting with .357 magnum or .327 magnum, typically used for harvesting deer or small predators with minimal risk of an unethical harvest due to caliber alone. 10 mm was developed to elevate semi-automatic service handguns in power range well above the popular semi-auto caliber choices of the 1980's (9 mm and .45 acp). It quickly fell out of favor due to being uncontrollable for most agents of the FBI, leading to the development of the less powerful .40 S&W. The 10 mm load is still carried today as a defense handgun against brown and polar bears, which should speak to the capability and ballistic potential of this power range, especially with suitably designed hard cast bullets.
.357 magnum (6 inch barrel)
10 mm auto (full size)
.327 magnum (6 inch barrel)
900-1,000+ fpe: This power range rivals weak rifle rounds in lethality, making these rounds overkill for personal defense against human combatants. The most common application of these calibers are for bear and moose defense in the polar region. Further, these calibers are borderline uncontrollable by even the most seasoned shooters. In most situations where these magnums would be deployed, a standard rifle caliber would be more effective, more accurate, and less unwieldy, making this power range nearly impractical for most purposes other than large animal defense. In training, one application might be inoculating experienced shooters against the effects of recoil, similar to training the use of the shotgun to increase recoil tolerance for rifle shooters.
.44 magnum
.41 magnum
.454 Casull
.50 AE
.500 magnum