Intro: What caliber a person feels is the “best” for any  particular usage in a handgun is a very complicated and touchy subject for firearms geeks.  It is also a potentially confusing topic to those who are just getting into firearms.  It is arguable that there is already a good caliber or two (or three) for any purpose.  However, emotions get involved in the discussion at times and opinions run strong.  Any handgun is a compromise; carrying around a rifle would be better. But it is impractical to take your AR out on the town .  So the question with a handgun becomes ‘what weapon can I comfortably carry and still have an effective means of defense?’   The decisions one has to make when carrying a handgun are the compromises between power, portability, fit, and capacity.  Everything is a tradeoff…


So what’s so great about the .45 acp?


Gather around and listen to a legend of our people. Once upon a time, a prophet, John Browning was given inspiration to bring forth the lord’s own preferred caliber. And the lord spake unto him, saying, “The number of the caliber shall be .45, No more and no less. .45 shalt be the number; 9mm shalt not count, neither count thou .40, excepting that thou then proceed to .45; .38 is right out. Once the caliber .45, being the blessed caliber, be reached, then, aimest thy pistol at thy foe, who, being naughty in My sight, shall snuff it.”  And Saint Browning raised the weapon up on high, saying, “O Lord, bless this Thy own preferred caliber that, with it, Thou mayest smite thine enemies and  blow them to tiny bits in Thy mercy.”  And the lord did grin, and the people did feast upon the lambs and breakfast cereals and power bars and barley beverages.


…Not really, but almost.

John Moses Browning was the greatest firearms designer ever.   Not that other designs or designers aren’t equally fantastic, but Browning had a depth and a proliferation of his designs that are STILL in the market over 100 years later.  So many of our current popular firearms owe their lineages to Browning it is astounding.  

In a discussion about ballistics there are a lot of physical forces at play.  Gravity, Velocity, Mass, & Aerodynamics, for example.  With the 9mm Luger and .45 Auto, you have two approaches to solving the same problem. Scientifically speaking there is not a vast difference in the kinetic energy figures between them, but from the momentum standpoint the .45 Auto has a clear edge. However, power matters on both ends (if recoil were not an issue we’d all be carrying a .44 Magnum).


The argument between the .45 ACP and the 9mm has always been big bullets moving slower with more momentum and bigger holes versus small bullets, moving faster, and more of them.  At the end of the day it is all a compromise. You can’t have both high velocity and a big bullet; well actually you can, we call that a 454 Casull, but fire too many of them at the range and you start talking like Rocky Balboa.  A ballistics chart, though, can never tell the full story.  To understand why we have the .45 ACP and why it will almost certainly never die, we need to take a history lesson.

The history of US military sidearms firing a metallic cartridge (as opposed to cap and ball designs) begins with the Colt Single Action Army (SAA) which began service in 1873 and was chambered in .45 Colt.  Everyone loved it, because it seemed to work better than anything else on the market at the time. The pistol and the cartridge were fantastically successful in the military and civilian world. But in 1892 the Army decided it wanted a more modern pistol that was double action with a swing out cylinder to speed up the reloading process which lead to the Colt M1892 and the .38 Long Colt Cartridge.  For a myriad of reasons all the firearms manufacturers had varied their designs between .36 and .45 caliber for years in search of the “sweet spot” ; in this instance Colt seemed to feel that .38 was the best size compromise for capacity and power in the new revolver.  The added benefit to the Army would be in less lead and powder usage.  In 1898 the US was engaged in the Spanish American war in the Spanish controlled Philippine Islands which the US won. Then in 1899 there was a Filipino uprising against US control and the Army encountered the Moro, indigenous Filipinos who became followers of Islam in the late 1300’s.  They had resisted foreign rule for 400 years.   As a form of Jihad these Juramentados, male Moro swordsman, attacked their enemies fully expecting to be killed. A juramentado was a dedicated, highly skilled individual who prepared himself through a ritual of binding, shaving, and prayer in order to accomplish brazen attacks armed only with edged weapons.

All of this bears telling because it is important to understand the mindset.  This is the Filipino muslim equivalent of a kamikaze.  They were supremely motivated and some sources state that they were also under the influence of drugs.  Multiple reports came out of the Philippines of soldiers emptying their weapons into these Juramentados and being killed by the swordsmen.  Clearly something had to be done. It was decided that the .38 caliber was not enough gun.  This led the Army and the Cavalry to decide a minimum of .45 caliber was required in a new handgun. The resulting cartridge, named the .45 ACP (Automatic Colt Pistol), was similar in performance to the previous .45 Colt cartridges.  After further refinement and testing the Colt pistol that Browning had designed was adopted as the Model 1911.  It seemed to work.  After 70 years of service, in 1985, under pressure from congress to standardize the US Military with other NATO forces on the 9mm caliber,  the military chose the Beretta 92/M9 chambered in 9mm.  However, the .45ACP held on in special units. Now as was the case then, reports from the field in Afghanistan and ISIS controlled areas maintain that the .45 is preferable to the 9mm against highly motivated, potentially drugged, suicidal attackers.   In 2017 the US Military chose a new sidearm from Sig Sauer still chambered in 9mm.


In the final analysis all of the ink spilled in the debate over whether the 9mm (.38 caliber), the .40, or the .45 is the best cartridge for X use doesn’t really matter.  No scientific study is really valid if the results from the field do not support the lab theories.  Many, many people who have went into harm’s way and have been faced with armed attackers seem to prefer the .45.  Their experience has to count.


One thing can be said with near certainty, the .45 ACP is supremely capable as a self defense round. The round is a lower pressure round than many other modern pistol rounds and therefore even though it lobs a large chunk of lead downrange, it is not often accused of having punishing recoil. Power wise it is a step up from the .40 S&W in factory loaded ammunition averaging somewhere around 456 ft lbs (~745 J) of muzzle energy.  Loadings can be had from somewhere around 350 ft lbs muzzle energy all the way to about 600 ft lbs (475 to 815 J) , which is from basic 9mm rounds to .357 magnum territory  


So it is a proven man stopper that can trace its’ lineage, in philosophy at least, back to the Colt Peacemaker.  It was designed in conjunction with the Colt 1911 pistol, which is legendary in its’ own right.  Why do we even have other self defense pistol cartridges?

First, there are two main variables firearms designers use when designing ammunition.  Bullet weight, and bullet velocity.  There are those who favor a slightly smaller bullet flying faster, and those who prefer a bigger bullet traveling a little slower.  Bullets poke holes, that is how they work.  The size of the hole matters, but so does the depth, and strangely, it seems when it comes to physiology the speed at which something makes the deep hole matters too.  So some designers and shooters favor velocity in the equation, where other say the size of the hole is more important.  The other factor is perceived recoil.  The actual mathematical recoil of a cartridge is just a number, but there is some physics at play that also deal with the recoil impulse.  This “recoil impulse” or recoil over time (as well as the ergonomics ,mass of the firearm, and the physiology of the shooter) can affect “perceived recoil.  What all this gobbledygook means is that just because the calculator says that a .40 S&W and a .45 ACP have almost the same actual recoil, the perceived recoil of the .45 is almost always portrayed as more “pleasant” because it is a lower pressure, and slower impulse round.  Writers may refer to some other rounds as having “snappy” recoil.  This means that the recoil impulse in question occurs over a shorter amount of time.  It is like a spike, instead of a gentle curve.  

Lastly, a designer must consider firearm size and capacity.  If a survey was done of hand sizes we could arrive at a certain perfect size of grip for the average shooter.  Firearms companies probably have researched this extensively.  There is a range of sizes that will fit the middle of the bell curve for the human hand.  Whatever ammunition you can fit into a grip this size is the capacity of the firearm you can sell.  In a .45 this is usually between 7 and 10, and in 9mm this is usually somewhere between 12-19. But those that lean toward the “a bigger hole is always bigger” camp believe in the .45’s innate ability for one shot stoppages trumps carrying over 10 rounds in one magazine.  Either way there is no denying that it is truly is one of the greatest pistol rounds ever produced, and it shows no signs of fading away.