9mm Vs. 40 S&W – Let’s End the Debate

We all agree on the best handgun caliber, right? Hardly. Travis Pike adds fuel to the fire with this discussion of 9mm vs. 40 S&W.


The 9mm vs. 40 S&W debate has firmly replaced the 9mm vs. 45 ACP debate. It started when most law enforcement, including the FBI, began switching from 40 S&W back to 9mm. What happened? Why is the 9mm becoming the be-all, end-all cartridge for defensive applications? We have a better understanding of how firearms work, and more importantly, how bullets affect the human body.

9mm Vs. 40 S&W – Stopping the Threat

For decades, the idea of stopping power existed. The idea was that a big projectile, moving rapidly, could hit a threat and shut them down within a shot or two. Stopping power pervaded the conversation but was never a solid science. For years people disliked the 9mm round due to a perceived lack of stopping power. The FBI even concluded in a report that “Handgun stopping power is simply a myth.” The famous 1986 Miami Shootout and subsequent findings cemented this idea in the eyes of the shooting public and led to the FBI Protocol that governs ballistic performance today.


Over time we discovered that stopping power didn’t provide an accurate assessment of handgun lethality. We discovered that projectile size was only important to a small degree. What was important was penetration, shot placement, and projectile expansion. A projectile needed to penetrate through 12 to 18 inches of 10% ballistic gel to reach the vital organs inside the body.

Projectile expansion caused by jacketed hollow points reduces the idea that a bigger bullet is better. Smaller rounds expand when they strike the body and grow in size. As they grow, they slow down but deal substantially more damage inside the body. Finally, we have shot placement, which ties to a shooter’s skills. You need to be able to direct rounds into an area where vital portions of the body exist, including the heart, lungs, and brain. When we talk 9mm vs. 40 S&W, which caliber excels in realistic lethality?

The Advantages of Modern 9mm

A modern 9mm round excels in the ballistic portion of handgun lethality. Modern jacketed hollow points expand and allow the 9mm round to grow in size substantially when it strikes a soft target. Most 9mm defensive loads penetrate within the 12 and 18 inch FBI standard. 40 S&W does the exact same and certainly meets the standards for an effective handgun round.

Shooting Competition

9mm excels as a defensive round for two reasons. First, it has remarkably less recoil than 40 S&W. This makes it easier to shoot and allows for faster follow-up shots. Additionally, 9mm uses a smaller bullet so firearms can carry more rounds. As you get into the realm of compact concealed carry firearms, these advantages become even more important. If you two rounds can both be effective, why choose one with higher recoil?

Also, it bears mentioning. 9mm is cheaper, therefore easier on the pocketbook when it comes to training.

What’s Wrong With 40 S&W

Nothing is wrong with the 40 S&W. It’s just a bit outdated. More recoil means slower follow-up shots, but I won’t pretend that the 40 S&W is some magnum caliber that’s impossible to control. It’s a little snappy, and that’s it. If you have a 40 S&W and you like it, there is no big reason to run out and trade it for a 9mm. On the flip side, if I was shopping for my first firearm or for a new firearm, I wouldn’t choose a 40 S&W.

In the 9mm vs. 40 S&W debate, we also have to talk about weapon size. 40 S&W works best in compact and full-sized duty firearms.

Once you get into smaller firearms, that snappiness becomes much harder to control. Guns like the Glock 27 can be tough to handle effectively compared to a 9mm Glock 26.

The 40 S&W does offer a serious advantage when it comes to hard barrier penetration. That’s where that extra mass and velocity excels. It can punch through glass, wood, and the like and retain more energy than 9mm. It’s a rare situation where that might be an advantage, but it’s worth noting.

Getting Frisky

Caliber debates can always be a great way to waste time! It’s often a much ado about nothing scenario. Use the caliber you want, as long as it penetrates deep enough, expands enough, and it’s something you can control and shoot accurately. However, if you want maximum efficiency, then the clear winner in our 9mm vs. 40 S&W is 9mm.

Agree or disagree? Comment below.


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Travis Pike is a former Marine Machine gunner who served with 2nd Bn 2nd Marines for 5 years. He deployed in 2009 to Afghanistan and again in 2011 with the 22nd MEU(SOC) during a record-setting 11 months at sea. Travis has trained with the Romanian Army, the Spanish Marines, the Emirate Marines, and the Afghan National Army.

He serves as an NRA-certified pistol instructor and pursues a variety of firearms-based hobbies.


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12 thoughts on “9mm Vs. 40 S&W – Let’s End the Debate”

  1. I don’t know much about 9 mm, but I used to carry a 44 magnum for years and the recoil as I got older was killing me. I went to the 40 Cal Smith and Wesson and I love this weapon! and I do conceal carry now and I can control it very easily because I am a big man I’m 6 foot two weigh about 250 pounds recoil doesn’t really bother me. I’ve shot a few 9 mm and they do have a lot less recoil, I can say That, but for me I love the 40 Cal Smith and Wesson! it’s my go to weapon! thank you.

    1. .40 S&W has more competent stopping power and matches or exceeds the .45 cal due to different bullet weights and configurations ( Lucky Gunner compiled a study of 1800 shootings and .40 cal performed better than .45 cal and 9mm and slightly better than .357 magnum) FBI tests showed it was a better performing round.

      9mm has gotten better due to better round configurations as well , but the reason many Law enforcement agencies are moving away from .40 cal is cost and the fact that smaller statured officers ( male and female) are entering the career field, many with little or no previous experience with firearms. These new officers like many novice shooters , struggle with firearm recoil and weight; .40 cals and .45s simply intimidate them.

      Add to it that our military and its special forces now prefer the 9mm ( GLOCKS and Sig Sauers) simply because 9mm x 19 ammo is very common world wide- allied nations and hostile forces have it on stock .

      I carried a Beretta 92FS on duty as a LEO , then the .45 Cal S&W 4506 then finally the GLOCK 22/23 in .49 Cal. The .40 was the fine middle point and as long as it is on the shelves at my local gun store and can be reloaded as well, I too am happy with it

  2. 30 years ago I would have disagreed with you and said 40S&W was superior. In 1994 it was. 357SIG was a player then too. Bullet technology has improved dramatically since then and thus 9mm, 40S&W, and 357SIG are now very comparable.

    1. Panheadsforever

      when discussing this issue it always seem to come down to “well with bullett technology”…. What no bullett technology for the 40S&W or 357 ??? Myself if someone is shooting at me I much rather have it be the 9mm instead of the 40S&W. Whatever works for the one shooting the gun is the best. Myself….I sold all of my 9mm and repaced with 40S&W,reload my own.

  3. I’m not a big fan of the 9mm! I’ve owned numerous guns in the past and don’t care the for the 9mm! What gets me, is a lot of people think it’s the do all,be all caliber! IT’S NOT! If anything it’s adequate at best. I’ll take a 40 s&w,357 Sign,10mm and yes the 45 acp any day!

  4. If I we’re looking for another gun it would most definitely be .40. Everyone moans about recoil. Learn to fire your gun. I m a small framed guy. If it was that snappy I couldn’t fire it consistently
    I have a g22 g3 and it’s fun to fire.

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  7. 9mm and .40 have both been popular for decades, with agencies switching back and forth depending on the need/latest fad. I have shot both with my Glocks (G17, G26, G22, G23) Sigs (P239 .40 & P320 .40) and most recently my Beretta APXs in 9mm. I prefer both rounds and would trust them both in any emergency. One would think .40 would have more stopping power but from what I hear 9mm has come a long way the last twenty years. Invest in both. Train in both. Be safe out there. Bang bang.

  8. I like both the 9mm and the 40…if I had to choose I’d go with the 40 caliber however I wouldn’t feel I was at a disadvantage with the 9mm…it’s just a personal preference…the 40 is more “snappy” then the 9mm but I’m of the opinion if you had to use it and your adrenaline is pumping I don’t believe you’d notice it…much like hunting…sighting your 30-06 or 300 win mag you feel it….when the cross hairs are on a deer you don’t…another advantage the 9mm has over the 40 is magazine capacity..fortunately I don’t live in a state where magazine capacity is restricted to 10 rounds which eliminates that advantage…I think it all boils down to what you’re comfortable with and can you hit what you’re aiming at…a hit with a 22lr will always be better then a miss with a 44 mag

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