9mm vs .40 Caliber: Reasons I Don’t Carry a .40 Smith and Wesson

Have you ever read an internet thread debating caliber? I have. They tend to degrade rather quickly to gun urban myth and B.S. For many people, the debate of 9mm vs. 40 Smith and Wesson vs. 45 ACP is simply too much to bear and so they don’t enter into the caliber wars. Completely understandable.

40 Smith and Wesson training ammunition currently retails for around $0.27 a round.

40 Smith and Wesson training ammunition currently retails for around $0.27 a round.

I have to be honest however, there are a lot of reasons why we should look at the caliber we choose in defensive firearms. Why wouldn’t you want to make the BEST ammunition choice for your defensive handgun?

I had some great caliber related questions in and following a class I taught this past weekend and I thought I would put some of the ideas that I find helpful in a podcast today.  

The circumstances in your life might be completely different and my decision might not work for you, but that isn’t the point. The point is to understand the thinking process I used when I decided to stop carrying .40 Smith and Wesson.

What Do I mean When I say, “40 Smith and Wesson?”

The phrase 40 Smith and Wesson has different meanings to different people in different situations.

It gets a bit confusing because Smith & Wesson is a firearms manufacturer. As a result, it is completely reasonable for someone to assume that when you say, 40 Smith and Wesson that you might be talking about a Smith & Wesson M&P 40, or a Smith & Wesson M&P Shield chambered in 40 caliber.

As reasonable as that may seem, my intention isn’t actually to talk about guns specifically today.  

Instead I want to talk about ammunition.

You see, what most people simply call a “forty” is actually called the .40 Smith & Wesson.  

This means that you can by a Springfield XD chambered in .40 Smith and Wesson. The GLOCK 22 was specifically made to chamber the .40 Smith and Wesson.  40 S&W guns are available from Colt, Kahr, Kimber, HK, FN, Beretta and the list goes on.

So how did a cartridge end up with the name of a famous gun manufacturer?

History of 40 S&W

The 40 caliber is typically seen as a result of efforts of the FBI, Winchester Ammunition and Smith and Wesson.  Cartridge has law enforcement roots in the FBI’s request to have a shoot-able alternative to the 10mm that performed better ballistically than the 9mm. Richard Mann talks about the history of the 40 Smith and Wesson in this article.

Let’s take a look at some of my history with the 40 Smith and Wesson and why I don’t choose it as a defensive caliber.

I’m Allowed to Talk 40 Smith Smack

Not because I’m any one special, but instead because I carried and shot a 40 Smith & Wesson for years.  I wish I had a round count of the number of 40 S&W rounds I have put down range.  I have no doubt that it is the caliber that I have the most experience with.  

This is just one of the good reasons I had to shoot .40 at the time and you might have some good reasons to carry a .40 right now.  My point of today’s podcast is not to disparage the .40.

There are plenty of reasons why someone might choose to carry a 40 Smith and Wesson, there just aren’t enough of those reasons that apply to me to make a 40 S&W a good idea.

Why I used to carry a 40 Smith and Wesson

For a long time I put a lot of energy into trying to become a successful competitive shooter.  I competed in USPSA matches around the country and had a great time while I was at it.  I was specifically interested in Limited Division and in order to score well, in addition to being able to shoot fast with accuracy, I needed to have a gun with a relatively high capacity and a caliber that would score Major Power Factor.

This STI Eagle 2011 in 40 Smith and Wesson was my concealed carry handgun for many years

This STI Eagle 2011 in 40 Smith and Wesson was my concealed carry handgun for many years

The two calibers that scored Major in Limited are .45 ACP and 40 Smith and Wesson.  The 40 S&W is a smaller bullet and so more 40 rounds than 45 fit into the same size gun. More ammunition in the magazine means less reloads and faster times.

This set of rules for USPSA competition made .40 the default caliber for Limited.  Anyone who was serious shot a .40 Smith and Wesson.  To me, at the time, it only made sense to carry the caliber that I spent so much time shooting.  So, I carried 40 Smith and Wesson.

Those were pretty compelling reasons for me at the time, however, I am no longer a competitive shooter and, I’m smarter.

Instead, now I am a defensive shooter who competes from time to time, so those reasons to carry a 40 Smith and Wesson no longer apply.

Even if I was a serious competitive shooter today, I think it would be a mistake to carry the 40 as a defensive handgun round.

I can say with certainty, using the rules of a game to dictate what you do from a defensive stand point is silly. 

It is fun to win a game, but it is better to win a violent encounter should you need to.

The above reason seemed like a good excuse to carry a 40 Smith and Wesson at the time, but I have clearly changed my mind.

Let’s look at the 5 reasons why I’m not likely to change back to the 40 as a defensive handgun.

5 Reason’s Why I Don’t Carry a 40 Smith and Wesson

Reason 1: I am not required to carry a 40 S&W

If I was a  law enforcement officer and I was required to carry a 40 Smith and Wesson it wouldn’t be the end of the world. I would carry it without worry. I would invest some additional time in training to make sure I was able to handle the additional recoil of the 40 S&W. Life would go on.

Here is a 40 Smith and Wesson cartridge (center) compared to a 45 ACP (left) and a 9mm (right)

Here is a 40 Smith and Wesson cartridge (center) compared to a 45 ACP (left) and a 9mm (right)

But I don’t work in LE or armed security.  My Friend Sherman House did work armed security before he became The Peoples Dentist.  Here is what Sherman thinks about the .40.

I work for, report to, answer to and am responsible for me and mine. and as a result, I get to make the choices that are the best for me without regard for all of the other worries that plague an agency.  I get to forget about politics, logistics, biases, and B.S. when I choose my firearm.

Many folks get caught up in what other people carry.  I don’t.  I’m the one that will have to defend myself and those that I love in a violent situation and so I am going to make the decision about the tool I’ll use based on what’s best for ME.  I think you should do the same thing.  Select the handgun and caliber that will perform best for you.

Reason 2:  Today, 40 caliber tends to be a solution where there is no problem

Modern bullet manufacturing has really taken the terminal performance of bullets to the next level and this has taken a serious bite out of the advantages that selecting a larger caliber used to have.

.40 Smith and Wesson was adopted in a time when bullets didn’t work very well.  9mm was questionable when it came to terminal performance.  That isn’t as much the case today.


It is only logical to consider that the larger diameter that a bullet is the more damage it will do when it enters a threats body cavity.  It has been this thinking that has ruled the roost in caliber selection for years.  You have heard it, “I carry a .45 cause there is no .46.”  If I were limited to a single shot gun, I might adopt this attitude.  But, none of us carry single shots (I hope.)

As a result, we have more variables to take into account when selecting caliber.  Instead of considering the medical damage that a single round causes we need to look at the amount of medical  damage that can be inflicted in a given amount of time.  The higher the rate of medical damage, the better.

This concept is called wounding capacity and it takes into account bullet diameter, recoil management, firearm capacity among other things. I talk about wounding capacity in detail here.

It really comes down to the idea that advances in bullet technology has calibers like 9mm performing as well as if not better than 40 S&W and 45 ACP projectiles of the past.

Reason 3:  Most Guns aren’t built to be 40 Smith and Wesson

The 40 S&W arrived on the scene after the development of the GLOCK 17 and the round was designed specifically to fit inside the frame of the GLOCK 17’s 9mm frame.  The cartridge was designed to fit into the gun but the gun wasn’t designed to handle the cartridge.

40 Smith and Wesson fits firmly in the middle between 45 ACP and 9mm

40 Smith and Wesson fits firmly in the middle between 45 ACP and 9mm

The recoil of the 40 Smith and Wesson is a god step up from the punch that the 9mm delivers to the gun and the shooter and throughout history we have seen some problems with the 9mm platforms with the .40 inside.  In some situations the gun just cant handle the forces as well and wears out sooner.  In other cases there have been catastrophic failures.

Either way you look at it, I would like to have a gun that is designed specifically around the cartridge that it is firing.  In many cases, the 40 Smith and Wesson chamberings were an after thought. I’m looking for more than that.

Reason 4:  Have you looked at the price of ammo lately?

Although 40 Smith & Wesson isn’t the most expensive ammunition out there, it isn’t the least expensive either.  9mm strikes a great balance when it comes to price and center fire handgun ammunition.  It is important to train with ammunition that has a similar recoil to the defensive ammunition that you use.   Recoil is an important part of learning to shoot quickly.  This makes the cost of training ammunition an important consideration.  Price is one of many logistical concerns  that we can use to help us make good decisions about our defensive ammunition.

The cost of ammunition  should never be the primary concern unless it means not having ANY ammunition.  The good news is that 9mm is less expensive than the 40 Smith and Wesson.  It is just a great bonus.




Cost per Round

40 Smith and Wesson




45 ACP








Reason 5:  Defensive caliber selection isn’t just about you.

My defensive handgun isn’t just for my use. I could handle shooting 40 if I needed to and you probably could too. That isn’t the point.  You see, it is probably wrong to call my defensive handguns, “my defensive handguns.”

This GLOCK is is my every day carry gun and it is chambered in 9mm, not 40 Smith and Wesson.

This GLOCK is is my every day carry gun and it is chambered in 9mm, not 40 Smith and Wesson.

My wife, who I spend a lot of time with, has access to OUR defensive handguns. It only makes sense. It is our job to protect our safety. My wife needs to be able to shoot our defensive handguns comfortably. They need to fit her hand. She needs to be able to manage recoil to make fast follow up shots. When we consider those facts 40 Smith and Wesson just doesn’t make sense.

If you have a choice, make it a good one and for most people that choice isn’t 40 S&W.

9mm provides reliable terminal ballistics, relatively high capacity, easy recoil to manage which all lead to a higher rate of medical damage than other categories. 

It really is the advances in terminal ballistics that have ousted the 40 Smith and Wesson.

Law enforcement agencies across the nation are making the switch from .40 toward 9mm and I would expect that it won’t be long before the FBI ( the agency that started it all) makes the change to 9mm.  

You shouldn’t be thinking about 9mm because the FBI is going to make the change, BUT you should be looking at 9mm due to the fact that it is an outstanding defensive performer.

Originally written by PaulCarlson

4 thoughts on “9mm vs .40 Caliber: Reasons I Don’t Carry a .40 Smith and Wesson”

  1. Good write up. I think you provide a lot of great reasons for why you carry the 9mm and not the .40. I really only disagree with a couple points, the first of which is the point of terminal ballistics. You say that carrying a bigger caliber would be an attitude you would adopt if we all were limited to single-shots. I disagree. A lot of people wave off bigger calibers in favor of the 9mm based on the logic of \”3 hits with 9 beats 2 hits with 40\”. That\’s true, but I also factor in the worst case scenario thinking, where the first hit I score may be the only hit I get. In my personal consideration, that doesn\’t mean I\’ll trade 11 of 9mm for 5 of .44 magnum, but 21 of 9mm (in 2 mags) vs 19 of .40 is often a tradeoff I make. Tied to that, I think really being a similar point, the same tech that has made 9mm better has also made every caliber better. There are deep penetrating 9mms that expand to over .60 cal, but there are also deep penetrating .45s that expand to an inch.

    That said, everyone has their own weighing of the many factors involved in caliber choice: terminal ballistics, capacity, familiarity, training considerations, platform, spouse\’s comfort, etc. Personally, I carry any of 9mm, .357 Sig, or .40 out of the same Glock. My proficiency is very similar between the three, so I worry much more about hitting the range at least once a week, performing regular maintenance, or carrying a spare magazine than I do about what caliber it\’s configured in.

  2. I think this is a great review and has help me determine buying a S&W 9mm over a S&W 40. All of what you said makes perfect sense. Thank you.

  3. This article does not seem to make the main point! Its not about the last round being fired in a gun fight (capacity) its about the first round fired (pick any caliber) that scores a hit in an area that really counts where taking away something that is needed for life support. As a medic, the first gun shot call I got was a very large (320lbs) man killed by one shot from a .22lr two barreled gun! It went through the fatty part of his right arm, entered the chest, bounced off the bottom rib, transverse the chest, and landed in his heart. This little .22lr, killed a very large man, well before he hit the ground! I have my favorite guns and calibers that I carry for different reasons and for different jobs. My little Smith 36/37 has been with me for more years then I care to admit. Easy to shoot, easy to carry, and a breeze to hide, they are a good choice for the job at hand. At the same time, my custom built 1911 in .45acp is something that I\’m sure will knock the poo outta bad boys very fast. This being said, if your shots are the first on target, where they need to go to stop life in the person during the bad things that started trouble, then you are the one that wins a fight. Pick any caliber that allows you to hit quickly where it needs to go, and allows you to carry all the time. Whatever you have with you, is better then what is in your gun safe at the time the SHITF. Above all, be safe!

  4. This is not a particularly strong or compelling argument.

    1 This \”not required to\” argument could apply to any caliber so it isn\’t a specific argument against he .40 on any specific merit or lack thereof.

    2. Again this is a generic argument that could apply to any caliber vs any other caliber, it\’s not a specific argument against the .40. Further the .40 has benefited from the same relatively recent advances in projectile development the 9 has so if the 9 has gotten better the 40 has probably gotten better too.

    3. Some guns may not be built for .40 but any others are and even those that originally were not, like the Glock 22, are now 4 generations and millions of rounds collectively fired removed from any initial shortcomings. There are plenty of choices available that completely nullify this argument.

    4.. 3 cents difference? C\’mon. If you can\’t afford that you probably can\’t afford to shoot in any quantity where it will matter anyway.

    5. Makes a good point for those who can only afford one handgun, but for others, if you are compromising your own carry weapon down to what a less physically or tactically capable shooter can handle, that\’s an issue in and of itself. Then perhaps more importantly, there\’s the fact that when you are carrying it, she doesn\’t have it anyway so she either has another handgun or has no handgun at all.


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