Caliber Selection – The Case for 9mm.

What caliber should I carry?  What factors should I look for when choosing a caliber for self defense? 

I hope to give you the information in this article to answer these questions for yourself and explain why 9mm was the right choice for me and maybe for you too.

Not all calibers are suitable for defensive use

First, what do we mean when we talk about caliber?

When we talk about caliber we are normally referring to the different types and sizes of ammunition, based on the diameter of the bullet.  It can be confusing because caliber might be expressed in metric, such as 9mm or in decimal inches, like .45 ACP.  It can get even more confusing because sometimes there can be more than one type of ammunition that goes by the same caliber yet they are completely different and cannot be fired from the same guns. (like .357 Magnum and .357 SIG)  We’re going to simplify it and just talk about the five main calibers for self defense in semi-automatic pistols.  This is NOT a discussion about “stopping power”.  All of the calibers below have shown effectiveness in real world defensive use and they comprise the vast majority of self defense options being carried today.  Revolver specific calibers are not being discussed here either, as the differences between the gun platforms make meaningful comparisons difficult.


The top five

  1. 9mm
  2. .40 S&W
  3. .45 ACP
  4. .380 ACP
  5. .357 SIG


These five calibers, especially the top three capture the largest percentage of concealed carry and police issued defensive ammunition in the country.  Each is adequate for self defense and capable of meeting the FBI standards set for defensive ammunition when using designated loads. I say these are adequate, because truly no pistol round is really GOOD at stopping a threat.  With minor variations all pistol rounds require multiple hits to reliably stop a threat, and the placement of those hits is as critical a factor as anything else. Each caliber has its positive and negative sides, and selecting the correct balance for you is critical to finding the caliber and pistol you want to carry.

Glock makes pistols for all common defensive calibers and are an excellent choice.
Glock makes pistols for all common defensive calibers and are an excellent choice.

 What are the traits of a defensive caliber?


A defensive caliber is a compromise between power, control, and capacity.  I’ll also add another two factors that I think need to be considered, those are cost and carry or conceal-ability.


Power is the measure of how much energy the bullet is going to deliver to the target.  More power usually means more penetration and a bigger wounds.  Increased power also brings with it more recoil, greater muzzle flash, and more noise.


Control is a measure of how quickly you can bring the gun back on target after firing a shot, and get off a second aimed shot.  While other factors play a role in this, generally lower power rounds with less recoil will allow for greater control and faster follow up shots.


Capacity is referring to how many rounds of ammunition a gun can hold.  Bigger bullets require bigger guns to hold the same amount of ammunition.  This adversely affects conceal-ability which is going to be an important factor for some people.


.357 SIG

357 SIG has a distinctive look, with the necked down casing
357 SIG has a distinctive look, with the necked down casing

Generally the most powerful loading on this list, the .357 SIG is a very effective round in use with many law enforcement departments and federal agencies across the country.  This round is kind of a hybrid, using a .40 S&W case with 9mm sized bullets. It fires bullets at very high velocities and they hit with a lot of force.  Recoil is sharp due to the high velocity, and the muzzle flash upon firing can be startling especially with shorter barrels.  It’s a good choice, but is probably the least common among civilian concealed carriers.  There are fewer low profile guns in this caliber than some of the others, and the cost and availability of the round can be prohibitive.  While prices will vary, at the time of the writing of this article common practice ammo was running .51 cents a round.


.40 S&W

.40 S&W is often considered to have the best, or worst qualities of 9mm and .45 ACP
.40 S&W is often considered to have the best, or worst, qualities of 9mm and .45 ACP

Currently the most common caliber in use among law enforcement, this round is often seen as a compromise between the high capacity of the 9mm and the greater power of the .45 ACP.  Another good round with plenty of guns available in this caliber, it offers a good mix of power and capacity in an easily carried gun.  Recoil can again be sharp and unpleasant for people with smaller hands, weaker wrists, or who just aren’t used to shooting that often.  Getting follow on shots quickly and accurately can be done with sufficient practice.  Common practice ammo is currently about .34 cents a round.


.45 ACP

The 1911 is a shooters favorite
The 1911 is a shooters favorite

A favorite among many shooters, this is the largest caliber on the list and is the original caliber for the much revered 1911 series of pistols.  The largest and heaviest bullet, it also is the lowest velocity in most loadings but still has significant power.  Recoil is heavier than in 9mm, but is mitigated somewhat by the generally larger, heavier pistols it is fired from.  Capacity in smaller, more easily concealed handguns is going to be much lower than most of the other options.  Recoil will also be much more noticeable in these smaller pistols.  Practice ammo for .45 ACP is currently around .35 cents per round.


.380 ACP

The .380 is a very small, light round that is considered right on the edge of defensive power
The .380 is a very small, light round that is considered right on the edge of defensive power

While I said that all the rounds on the list were “adequate” for self defense, .380 ACP is only marginally so in most loads.  With the proper bullet selection it can perform well enough but it is the lowest power and lowest performing round of the bunch by a wide margin.  The .380 has one great advantage however, it can be chambered in the smallest, most easily concealed pistols of any caliber on the list.  Pistols chambered in .380 are small enough to be carried in the pocket of normal pants (with a proper holster) requiring no changes to your wardrobe in order to conceal it effectively.  While not issued by any law enforcement agencies as a duty caliber it is frequently carried by police as a backup weapon and by ordinary civilians who don’t want to make major changes in order to carry a pistol.

Some of the smallest pistols available, like the Ruger LCP come in .380 ACP
Some of the smallest pistols available, like the Ruger LCP come in .380 ACP

As much as the small size of the guns available for this caliber are it’s greatest strength, it brings with it some negatives of its own.  Due to their small grips and light weights these guns can have more perceived recoil than more powerful rounds fired from heavier guns.  The sights on these guns are also often very basic, and the small frames make holding these guns in a stable grip more challenging.  This can lead to follow up shots being more difficult to acquire than you might otherwise think.  Practice ammo in this caliber is about .42 cents a round, much higher than you might expect for such a small and low power round.



The Glock 17 is one of the most common weapons carried for duty and self defense
The 9mm Glock 17 is one of the most common weapons carried for duty and self defense

This is the most popular handgun caliber in the world, and it is in use by many law enforcement departments around the country.  It is the most common round carried by civilian concealed carriers as well thanks in part to the enormous number of quality pistols that are available for it.

Firing a small, but high velocity round it has good power but low recoil, with perceived recoil being about half of most other calibers on the list.  Pistols chambered in 9mm normally have the highest capacity compared to other pistols of the same size, and 9mm pistols can be had that are only fractionally larger than even some of the smallest .380 pistols.


Low recoil lets you get back on target quickly and follow up shots are the easiest to come by.  Practice ammo averages around .24 cents per round currently, the lowest cost on the list by nearly a third.


Why I think 9mm wins


All of the calibers on the list make a good choice for defensive carry.  Factors such as your size, strength, any physical handicaps, and relative experience level might make one or the other calibers more suitable for you.

All other things being considered however, no matter how good you are shooting one of the other calibers you could be better with the same amount of practice firing the 9mm.

The combination of low cost, low recoil, and high capacity make 9mm a winner for me.

The cost differential between 9mm and the other offerings mean I can shoot in training between 30-100% more than other calibers.  To put that in perspective if I was scheduled for a training class that fired 300 rounds ammunition would cost me approximately $72.  Shooting that same course with other calibers would bring my ammunition bill between $102 and $151.  That’s a significant price increase, and if my training budget were fixed I might be able to shoot twice as often with 9mm compared to .357 SIG.

Monthly range sessions now become bi-weekly range sessions, keeping skills sharper.  Softer recoil means I can shoot longer with less fatigue to my hands.  I can shoot drills twice as often for the same cost and without wearing myself out. Follow up shots are faster and more accurate for the same amount of practice compared to other calibers.  9mm also offers a lower physical threshold for shooters.  This may not be a concern for the young and healthy but for elderly shooters, women, or those with disabilities it may be the ONLY good defensive caliber they’re capable of shooting with any reliability.

In short, 9mm lets me be a better shooter, faster, more accurate. The skills of the shooter mean more than the size of the bullet, and whatever helps in that regard is a winner.


UPDATE: Just days after posting this article the blog The Truth About Guns reported on the FBI decision to switch to 9mm.  Quoted in the article is their reasoning, identical to the points I’ve outlined here.

“It’s not that the .40 S&W failed to deliver the terminal performance they wanted. It’s just that the new breed of 9mm ammunition can deliver similar performance without the generally snappier recoil and the accelerated wear (on both pistol and shooter), at a more affordable price. The fact that the new pistols can house more of the cartridges in the same sized gun is an added bonus.”


2 thoughts on “Caliber Selection – The Case for 9mm.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s