When it comes to choosing a handgun caliber, we could write for days and days. For some folks, if it doesn’t start with a “4” (.40SW and .45 ACP), you mine as well not bother. Others will say more people have fallen to a .22 LR than any other caliber. At the end of the day, the truth lies somewhere in the middle.
Let’s take a look at a few calibers or cartridges that will be what most semi-automatic carry guns come chambered in. What is the caliber in a gun? Simply put, caliber is the bore diameter, but for most of us, caliber is the term for a cartridge. That is the total package, bullet, case, powder, and primer all combined to a standard.
When choosing a handgun caliber, the ammunition choices need to be easy to find, have good lethality, reasonable recoil, and be able to give the firearm good capacity. Revolvers are great, they have their place, but most folks have turned to carrying a semi with a higher round count and comparable ballistics. We are also drawing the line in the sand at the first caliber that can meet the minimum FBI requirements for lethality.
.380 ACP
This is the most petite round capable of genuinely meeting the minimum standards that the FBI put out when searching for a new service gun in 2015. Penetration, Permanent Cavitation, Temporary Cavitation, and Fragmentation are all factors in this rating. The .380 meets these standards in the best-case scenario. Let's look at why you may want to carry one but also may not.
The .380 ACP is generally chambered in Mircocompact handguns which can be easily carried and concealed. The guns chambered for this round are typically able to be put in a pocket or ankle holster without noticing a considerable amount of weight or feeling burdened. Those are the ups. The downs are, with micro compact 9mm prevalent, a shooter can carry a much more capable gun in relatively the same package. A .380 is the minimum for carry concealed guns and the 9mm is the most popular round. Guess where most people go with that info.
9mm
You may hear this round called the 9mm Luger, 9 x19mm or the 9mm Parabellum. They are all the same and are more commonly known as the 9mm. A short time ago, a lot of people thought that the 9mm was too “weak” to be a reliable carry gun. The US Military, later the FBI and most Law Enforcement agencies understood the value of this round early on. Even after straying to other rounds, agencies and citizens alike have migrated back to the 9mm.
Why would you want to carry a 9mm. Well, with modern ammunition, a shooter can have a compact, sub-compact or micro-compact gun in 9mm. This small gun will have power to spare along with double-digit capacity. The same cannot be said for the 10mm based rounds like (.40 S&W,10mm Auto) or the venerable .45 ACP.
When it comes to the guns chambered for 9mm there is a flavor for everyone. Along with the compact, sub-compact and micro-compact sizes listed earlier, you can also carry a full size 9mm with capacities in the twenty-round range. With so many 9mm in circulation, ammunition is the least expensive of all the rounds listed and the guns span the range of downright cheap to high-rent customs. There is a lot of good in the world of 9mm and not a lot of downside.
40S&W
This round was the standard one round for everything answer for about fifteen years. That seemed to wrap up about five years ago or so. When the 9mm got its second wind with new contracts spanning many agencies.
The .40 S&W seemed to just drop right off. Part of that was the switch from .40 to 9mm by the FBI. What a .40 did well was blend the “stopping power” of a .45 ACP or 10mm Auto into a similar recoil profile and firearm capacity of a 9mm. The .40 S&W does a lot well but nothing exceptionally.
Generally, you will need a bit larger frame gun to house the .40, and that gun will recoil more than a 9mm. The price per round is a bit more, and the gun will generally wear out faster under that increased recoil. With all of that said, a .40 is still a very capable caliber in any of the reliable, reputable guns it’s chambered in.
.45 ACP
The Ol’ Warhorse. The 45ACP was designed at a time when a Cavalry charge of horse-riding soldiers was a real possibility in combat. This round was designed to send a big bullet at a reasonable speed and stop said horse. It was THE semi-auto round for almost a century, until 1985, when the US Army adopted the Beretta M9 in 9mm for the official service sidearm after a long testing process.
This has been consistent throughout the modernizing of the US military; as ammunition improves, overall stopping power and often long-range capabilities are replaced by more efficient rounds housed in firearms that have higher capacity and tend to be more “shootable” than their predecessors.
The .45 ACP is a great round; it delivers a relatively slow velocity, large caliber, heavy bullet with highly effective stopping power. But to do all that, it has to have a big casing, and with the enlarged size, guns chambered for the .45 tend to have lower capacities.
There are lots of folks who feel no need to have the higher capacity and modern capabilities of current 9mm offerings. They feel when it comes down to needing a situation to stop that very second, every other round comes second to .45 ACP. This round will not go away even after more than 110 years in the spotlight. But it is expensive to shoot and requires a larger framed lower-capacity firearm to bring it to bear.
Last Shots
There is no 100% perfect choice for a handgun caliber, but with that, we have compared everything to a modern 9mm loading. This is because the 9mm sits in the lead with inexpensive ammunition, a multitude of available firearms and styles, ubiquitous military and police use, and having enough lethality with lower recoil. All of that means a shooter can train more, with the gun of their choosing, and have enough firepower never to be under-gunned, but not so much that all of that work becomes not fun due to recoil. Any of the calibers on this list are fine, but likely none are as fine as the nine.