Why Everyone Should Own a Full Size 40 Caliber Pistol

A .40 caliber? Pffft That caliber is dying. Get with the times Dan and get a double stack 9mm 2011 with a red dot optic…

Why Everyone Should Own a Full Size 40 Caliber Pistol

“A .40 caliber? Pffft That caliber is dying. Get with the times Dan and get a double stack 9mm 2011 with a red dot optic…” (For the record, my daily carry gun is a 9mm Sig Sauer but my SHTF gun is a full size .40 - I’m going to tell you why below. Oh and neither has a red dot but that is a topic for another article…)

A few months back I wrote a blog post titled: “What’s in Your Wallet” about my personal ammo wallet and the calibers I’m accumulating at AmmoSquared. One of those calibers is 40 S&W Practice. This is not a very popular round these days as you might have noticed. It isn’t extinct of course, but its popularity has drastically declined over the past 5-10 years.

First of all, to kick off this article and get some hard numbers, one tool I like to use to check out how popular certain calibers are is Gunbroker. (I did this a lot when we were trying to find new and obscure calibers to add to our ammo catalogue, which was not a good business decision, as we now know!) Anyway, if you visit Gunbroker.com and browse to a particular type of firearm, in this case I’m interested in semi-auto pistols, the menu looks something like this:

What I do next is scroll down to the filters on the left side until I can see calibers. Like this:

On this particular day, March 3rd 2023, there were 59,078 pistols available in 9mm, then another 11,897 in 22LR, and on down the list until we see that 40 S&W squeaked into the top five with 4,590 pistols. So 40 S&W pistol volume available on Gunbroker is only 7.7% of the 9mm pistol volume… remember that percentage, 7.7%.

Here is something else I found really interesting…

The last time I ran a report on our caliber volume was a couple months ago in order to determine what SKUs to discontinue. At that time we were doing 31.4% our total volume in 9mm Practice and only 2.45% of our volume was in 40 S&W Practice. So said another way our 40 S&W Practice volume was 7.8% of our 9mm Practice volume! Weird.

How uncanny is that?

The two should be a good representation of the popularity of 9mm over 40 S&W. So knowing all this, why do I still own a 40 caliber pistol and even go so far as to say everyone should have one?

I’ll lay out my logic and maybe you’ll agree with it and maybe you won’t. That’s the amazing thing about opinions… they're like… uhm.. noses… everyone’s got one and they’re all different.

Ding-Ding time for a Caliber Debate!

Bullet Construction

Let’s start with the most divisive right up front. The argument is that 9mm is just as good as 40 caliber now with modern bullets. That is why the FBI switched over to it and why many (most?) law enforcement agencies are switching too.

My response to that is simple - if the bullets in 9mm are better then so are the 40 caliber bullets. An HST or a Gold Dot isn’t suddenly less effective in a 40 then in a 9mm, right? There is no question that if you push a bigger bullet faster, it will be more effective. The only question when it comes to handguns is, does it matter in the real world? Lot’s of people say “no”. I say, why not take the bigger bullet? This is a game of compromise and some people want to compromise here while others would rather compromise on capacity which I’ll cover next. For now, head to head, a 40 is bigger and heavier so it wins this round.

Advantage: 40 S&W

Magazine Capacity

In just about every gun that is made as a 9mm and a 40 S&W, the 9mm will hold 2 more rounds. A typical full size 9mm like a Glock 17 has a 17 round capacity while the Glock 22 has a 15 round capacity.

My opinion here is that 2 extra rounds only matters for small capacity guns. If you have a concealed carry gun (like I do) that only holds 12 rounds of 9mm, then switching to a 40 in the same gun is bigger percentage difference then the Glock 17 / 22 example above. So said another way, 40 is great for full size guns with higher capacities already - not so great if you are already trying to squeeze as many rounds as possible in a small frame guns. In that case pick the 9mm.

Advantage: 9mm

Recoil Control and Follow-up Shots

There is no debate that a 40 recoils harder than a 9mm. The argument goes that since a 9mm recoil is lighter, a shooter can get back on target and get the next shot(s) off quicker.

I haven’t done the testing personally and I’m sure there is someone out there that has, but we’re talking tenths of seconds at best. With practice I can hammer a pair of 40’s out faster than some shooters can do with 9mm. So honestly this one comes down to proficiency, and since we are talking about recoil I would also say gun size. A tiny concealed carry gun is going to be much harder to control in a 40 then in a 9mm. A full size gun in 40 on the other hand, I have to believe the split time is negligible if the shooter is proficient with the 40. Exhibit A: Jerry Miculek with six shots of 44 magnum in 1 second

Advantage: 9mm for small guns and/or less proficient shooters


There is no question on this one, 9mm is cheaper. Since it is produced in such great quantities compared to just about every other round out there, it is going to be the cheapest in normal times. Currently our 40 S&W Practice is $0.46/rnd, but our 9mm Practice is averaging $0.34/rnd, so 26% cheaper. The theory goes, that since 9mm is cheaper, folks can afford to practice with it more. That is true. Also government agencies and pencil pushers like the fact that is cheaper. I’m going to go out on a limb and say that is weighted pretty heavily when a department or government agency decides to adopt 9mm over 40 S&W. Why go with a more expensive round, if this one will do the job just fine?

Advantage: 9mm


This is where things get a little squirrely. Now that we’ve all lived through yet another ammo crunch, we’ve seen some things haven’t we? In my mind, 9mm is the victim of its own success. During normal times - like now, 9mm is pretty widely available. You can find it for sale online or at your local gun store. BUT as we all saw recently when supply is limited and demand skyrockets, everyone and their third cousin twice removed wants 9mm. If 12 people want 9mm and 1 wants 40, then the 9mm is going to disappear first (unless the gun store carries 12x more 9mm… but that usually isn’t the case).

During the ammo shortage, 9mm disappeared first then was not available at all from our distributors… but I could find plenty of 40 S&W for a long time and believe it or not even 357 Sig. If you are stockpiling then this is less of a concern of course.

Advantage: Mixed (Normal Times vs Shortage)


This finally brings me around to my opening statement: Everyone should own a full size 40 cal pistol… but I will add the following: WITH a drop in 9mm conversion barrel (and if you are really a gun geek like me, a drop in 357 Sig barrel as well).


Because this combo covers all of the advantages of the 9mm and the 40 and has no drawbacks (unless the pistol you want doesn’t have that option). I know at least the big three: Glock, Sig and S&W all have full size pistols with drop in 9mm options.

This is why my main “go to war” full size pistol is a 5” S&W M&P 2.0 originally chambered in 40 S&W with a drop in 9mm conversion barrel from Apex and a somewhat hard to find .357 Sig barrel from KKM.

This way I have the slight edge in power and penetration from the 40 S&W or 357 Sig when I want it, but the lower recoil and cheap practice rounds available in 9mm when I want that. If there is an ammo shortage and I can’t find 9mm for some reason, I can always buy 40 S&W or even 357 Sig. Also, since I’m polyarmorous (I love many different calibers) I can take one “main” pistol to the range and mix it up when I get bored with a 30 second barrel and mag change.

Since 40 and 357 Sig share the same case diameter it makes them an easy barrel swap away, but 9mm is smaller so you will need a barrel and 9mm specific magazines. Also because of that, you can’t go from a 9mm pistol and drop in a 40 barrel, it won’t work, it has to be the other way around: a 40cal pistol and a 9mm barrel.

Since many police agencies are moving away from 40 caliber you can pick up a cheap police trade in pistol and get a new 9mm barrel for it, so you have the best of both worlds. Don’t let the cult of 9mm fool you into thinking 9mm is the only handgun round on the planet and everything else is blasphemous. Calibers aren’t marriages! Explore and play around with other calibers… don’t be afraid to be polyarmorous like me!

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