How To Pick Between 9mm, 40, or 45 ACP For Self Defense

When you think about choosing a weapon for self defense, you’ll want to make the best choice possible. In regards to handguns, there are a lot of options out there, but some of the most popular models are 9mm, .40, or .45 ACP.

To decide whether you want a 9mm, 40, or 45 ACP for self-defense, you need to consider the magazine capacity, reloading speed, recoil, cost, and your own comfort with the firearm. Generally, the most important consideration is your proficiency with the caliber.

Below we have a brief comparison between 9mm, .40 S&W, and .45 ACP and why you would want each one. They each have their own quirks that make them suited to different users.

First, The Basics

Firearms are classified by their caliber, which is the diameter of the widest part of the bullet.

A bullet is the projectile that is fired by a round of ammunition.

Firearm ammunition in its entirety is referred to as a cartridge.

A magazine is the ammunition storage.

There is a general understanding that shot placement is more important than the caliber shot. (The caliber that you choose is important though, hence this article!) Therefore, firearm proficiency is the most important factor in good self-defense. Here is a video with tips on how to improve shooting a pistol:

What is a “9mm” and Why is It Good for Self-Defense?

The term “9mm” is referring to the caliber of a bullet, meaning that the diameter is 9mm. Typically, when someone is talking about a “9mm” gun, they are referencing a semi-automatic pistol that fires 9mm caliber bullets.

Some of the best 9mm models for self-defense are:

Walther PPQ M2: The best part of this gun is the trigger, one of the smoothest you’ll find in a handgun. This comes in either a 4 or 5-inch barrel. Although the 5-inch barrel is great for aiming, both lengths will be an excellent choice. This pistol has striker fire action and an extremely light trigger pull. That makes it’s a perfect beginner’s handgun for those who aren’t used to throwing their weight behind a firearm.

CZ 75 SP-01 Tactical: This is both a great home defense handgun and a favorite for firearm enthusiasts. The SP-01 Tactical variation is a little different with a side-in-frame design that offers recoil management. This is perfect for shooters who want a comfortable grip. Because of the fixed night-sight system, you’ll be able to see your target clearly no matter how dark the night, which is a great feature for self-defense! A comfortable grip, sharp accuracy, and a smooth trigger pull put this handgun at the top of most lists. Plus, it’s affordable!

Beretta M9: The Beretta M9 functions as an all-purpose handgun. In 1985, it became the sidearm of choice for the United States Armed Forces. That definitely speaks to its reliability and effectiveness. It features a unique 3-Dot Sight System for quickly zeroing in on your target. It’s designed for quick tactical reloads in combat scenarios, which can be a great asset for self-defense. An extra plus is it’s lightweight and easy to handle.



  • A great benefit to using 9mm semi-automatic pistols is that they typically can hold a large number of rounds, which is very important in quick self-defense situations. You do not want to be wasting time trying to reload your gun when your life is on the line. The average magazine capacity for 9mm is 15 bullets per magazine.
  • That being said, 9mm guns are easier to reload. So, if you do need to reload in a self-defense situation, this will save you crucial time and energy.
  • 9mm guns are relatively small and therefore, are great for concealing. (But first, make sure to get a Concealed Carry Permit!)
  • They’re extremely common and popular! This means that there will be no shortage of accessories and advice on how to use your 9mm.


  • They are prone to jamming, which is not good for life-and-death situations. Be very familiar with how to unjam your gun if you’re going to be using a 9mm for self-defense.
  • Because the bullet is lighter, there is concern about its “knockdown power.” However, in a self-defense situation, this gun has enough power to stop an attacker from causing you harm. It also creates a narrow wound cavity.

What is a “.40 S&W” and Why is It Good for Self-Defense?

The “.40” refers to the caliber of the bullet, being .40 inches in diameter. When talking about a .40 S&W, most people will drop the decimal and just say forty. The S&W stands for Smith & Wesson. This can also be referred to as just a “40.”

“First developed in 1990, the .40 S&W is one of the newer cartridges on the block. It was developed as a joint effort between Smith & Wesson and Winchester, who were tasked by the FBI to come up with an effective round to replace their 9mm and .38 Special cartridges.”


After two and a half decades of use from the FBI, the .40 S&W was retired. Instead, the FBI returned to utilizing 9mm after research and development on new 9mm ballistics proved to be the most useful. The U.S. Army did consider adopting the .40 S&W cartridge but ultimately decided against it as they also found the value in the new 9mm ballistic studies to be substantially better.

Some of the best .40 caliber models for self-defense are:

M&P40: The M&P pistol is designed for very comfortable shooting. With this handgun’s build quality, expect a long service life and reliability. This has a 9mm model as well, but the .40 has been known as a workhorse pistol. It’s always been reliable and accurate, even since its initial first release.

Sig P320 Compact .40: The Compact gives you everything that the full-size has to offer, but in a more compact package (thus the name). This makes it ideal for daily carry. There even is a specific Carry model, which has a full-length grip and adds extra magazine capacity. Both the Compact and Carry would make great self-defense handguns.

Sig P229R .40: The all-steel frame is designed to soak up the recoil better. It’s a very common police-issue pistol, used by detectives and plainclothes officers. This is not considered a small handgun but is able to be carried daily with a strong and durable belt. It does have the classic Sig Sauer DA/SA operating system. Since it’s fairly big and heavy, the .40 S&W has a little less snap than a smaller handgun.



  • .40 S&W is powerful and is very capable of stopping an attacker (much more than 9mm).
  • The caliber is the same size as a 10mm but the .40 S&W is considered easier to handle.
  • It has a proven track record of success with the FBI.


  • Some people have complained that it is underpowered compared to the amount of recoil it produces.
  • Not recommended for inexperienced shooters.
  • Not commonly used, which can significantly reduce the availability of ammo and accessories.

What is a “.45 ACP” and Why is It Good for Self-Defense?

The “.45” refers to the caliber of the bullet, being .45 inches in diameter. When talking about a .45 ACP, you drop the decimal and just say forty-five. ACP stands for Automatic Colt Pistol. This can also be referred to as just a “45.”

“The 45 ACP caliber has earned the reputation of being a very effective combat pistol cartridge because it combines accuracy and stopping power against human targets.”


Some of the best .45 ACP models for self-defense are:

FNX-45: This gun packs a serious punch, and despite its size, it remains fairly steady when shooters deal with its recoil. It stays pretty up to par with most 9mm pistols as well. It’s got 3-Dot Night Sights which helps the user accurately focus on targets even during the darkest of nights. Most people consider the best part of the gun as its inclusivity. The FNX-45 is fully ambidextrous in safety levers and magazine releases. Plus, there are two mounting spots for adding a red dot. Without a doubt, this is a versatile firearm that is adaptable to any environment for any user.

Springfield XD MOD2: The ‘Grip Zone’ on this gun not only makes it comfortable to hold but also helps you control the recoil. Given it’s a .45 ACP with a 4-inch barrel, it has a great capacity for a compact. The shorter barrel also makes it a great lightweight option, perfect for close-quartered defense situations. The Melonite finish gives a complete corrosion resistance while the barrel length makes it a fairly easy handgun to conceal.

Colt 1911: This handgun can have some pretty significant drawbacks depending on what you’re looking for. It has a low magazine capacity, it’s fairly heavy, it’s larger than a typical handgun, and it’s not all that reliable. However, it also has some substantial pros, enough to give the Colt 1911 a serious following. Every 1911 has an upswept beavertail grip safety that requires the user to grip it firmly to be able to fire the gun. This feature makes it much harder to have an accidental misfire and is therefore great to have as a home defense gun in a home with young children.


  • The .45 ACP has a significantly better reputation for its “knockdown power.” It was used in the military for decades as their sidearm of choice until in 1985 they switched to using 9mm.
  • Given its size, the .45 ACP produces not only a bigger hit to your attacker, but will also leave a much larger wound cavity upon impact of the target.
  • Just like the 9mm, these models are very common and popular.


  • The typical magazine capacity for a .45 ACP is 7-8 rounds. Extended magazines can go up to 10 rounds and one model reaches 15 rounds (to hold 15 rounds it is generally too big for concealed carry).

Directly Comparing Recoil

Recoil can also be called the “kick” or “kickback” from a handgun. Essentially, it is the force exerted by a fired handgun upon the user.

CartridgeBullet Weight (gr)Bullet Velocity (fps)Propellant Weight (gr)Handgun Weight (lbs)Handgun ReferencedRecoil Energy (ft lbs)
9mm11511277.51.4Glock 174.6
9mm12410615.91.4Glock 174.5
9mm1479966.31.4Glock 175.5
40 S&W16510085.81.5Glock 236.5
40 S&W1809205.31.5Glock 236.3
45 ACP18592582.4M1911A24.4
45 ACP2308485.52.4M1911A25.4

Felt Recoil Energy

The handgun you’re using, the way that you hold it, and even the weight of your arms can all influence how much recoil you’re actually going to be subjected to. While calculating your ammo’s recoil energy can be educational, it’s not an exact measure of how much kick you’re going to experience.”


In general, considering the numerical recoil energy and overall opinions of the felt recoil energy, a 9mm will almost always have the least amount of felt recoil energy compared to the .40 S&W and .45 ACP.

Some people feel that the amount of recoil they feel from a gun does not match the power of the shot itself. It’s a good idea to try out each of these guns at a shooting range and see which one feels right for you.

Directly Comparing Costs

To get proficient, you need to practice and that means you need a lot of ammo. Ammo costs money, so the cost of ammo needs to be considered in comparing guns.

There is standard ammo and then premium ammo. As you can expect, premium ammo is more expensive, typically no less than a dollar per round.

Note: Ammo prices have gone up significantly in 2021.

These are the current averages as of June 2021:

Average Standard Ammo Cost
9mm$0.40 per round
.40 S&W$0.50 per round
.45 ACP$0.60 per round

Check out this link to see the history comparison of 9mm, .40 S&W, and .45 ACP prices per round.

A brief summary of ammo trends: 9mm are pretty much always the cheapest out of these three options.

What Do The Police Use?

“Generally, all law enforcement officers in the United States are armed with semi-automatic pistols at a minimum.”


Currently, the majority of the U.S. police force (and most law enforcement agencies) are using agency-issued 9mm semi-automatic pistols. Although, .40 S&W and .45 ACP are still being offered as additional sidearms, and they both have been used as primary firearms in the past.

Different departments have different regulations and options for sidearms, so there is no definitive answer for “what gun does the police use?” That being said, one of the most popular sidearms that police officers are carrying is 9mm Glocks.


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Matthew Osborn

Matt is an entrepreneur who has created and successfully exited multiple companies and brands. Now, he dedicates his time to Legionary, where he produces content on guns, family, and freedom.

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