Is A 9mm Handgun Big Enough?

October 3, 2021
Is a 9mm Handgun Big Enough?

Developed by Georg Luger in 1901, the 9mm is the world’s most popular centerfire semi-automatic pistol cartridge. Chambered in such iconic weapons as the Heckler & Koch MP5 and IMI UZI, it’s also one of the most widely used cartridges in submachine guns. However, despite its widespread adoption and popularity, even some experts still question whether a 9mm handgun is powerful enough to meet the self-defense and duty needs of the private citizen and police officer?

Stopping Power: The Never-Ending Debate

Whether you’re interested in home defense or concealed carry, your choice of caliber and ammunition type play an important role. Stopping power refers to the ability of a bullet to incapacitate a determined human aggressor. The topic of stopping power is highly controversial and has been the subject of constant debate. Those who favor big-bore cartridges stress the importance of caliber and weight. Proponents of lightweight, high-velocity bullets emphasize the effect of kinetic energy and the sonic pressure wave (hydrostatic shock). Some extol the virtues of magnum revolver and pistol cartridges, preferring a combination of weight and velocity. It’s important to remember that handguns, as reactive weapons, are by definition a compromise. Police departments issue handguns to police officers to meet unexpected threats, which is why private citizens carry semi-auto pistols and revolvers. Handguns are convenient to carry, being relatively lightweight and portable. If you intend to meet an anticipated attack, it’s best to choose a shoulder weapon, such as a centerfire rifle or shotgun, which is generally more powerful. Carrying long guns daily, however, is not usually a practical solution.

Shot Placement is Essential But Not Enough

Regardless of caliber, ammo type, or weapon, shot placement is critical to incapacitation. If you don’t place your shots properly, you can’t expect to stop an attacker. However, while an essential criterion, shot placement is not a sufficient one. If a perfectly placed shot fails to reach and disrupt vital structures, it may not reliably stop the attacker.

Incapacitation: Penetration and Permanent Cavity

For a bullet to cause physiological incapacitation, it must disrupt the central nervous system. This may be caused directly by damaging the brain or cervical spinal cord or indirectly by depriving the brain of oxygenated blood. Under the stress of combat, you can’t expect to achieve the kind of pinpoint accuracy that allows you to damage the CNS directly. As a result, tactical training emphasizes aiming for center mass or the thoracic triangle. This increases hit probability and prioritizes indirect CNS disruption by damaging vital organs and major blood vessels, such as the heart and thoracic aorta, to cause hemorrhage.

FBI Penetration Standards

The bullets you select must achieve sufficient penetration to damage these vital structures from a variety of angles. The FBI considers 12” in 10% calibrated ordnance gelatin to be the minimum penetration acceptable. Optimum penetration is 15” and the maximum is 18”. In establishing these performance standards, the FBI also considered the possibility that a bullet may have to pass through a raised limb, such as a forearm. If an assailant is aiming a gun at you, this may become relevant.

Bullet Expansion

Once you’ve chosen a defensive load that penetrates deep enough, the best way to increase the effectiveness of the ammunition is to increase the diameter of the permanent wound cavity. The permanent cavity is the hole created by the bullet’s passage as it crushes and destroys soft tissue. Caliber, bullet shape, and frontal surface area all affect the quantity of soft tissue crushed and the diameter of the permanent cavity. Jacketed hollow points that expand increase the frontal surface area, increasing the permanent wound cavity diameter while also transferring more kinetic energy to the target.

Modern Ammunition

Modern 9mm defensive ammunition

In 1986, the FBI used a variety of handgun cartridges, such as .38 Special, .357 Magnum, and 9mm Luger. In the infamous Miami shootout, two FBI agents were killed and five wounded so the Bureau began to re-evaluate its weapons and tactics. After establishing new criteria for determining the effectiveness of ammunition and testing different calibers and bullet types, the FBI adopted a reduced-pressure 10mm Auto load and the Smith & Wesson Model 1076 in 1990. Ammunition technology has advanced significantly since then. Modern 9mm defensive ammunition, jacketed hollow point bullets, reliably achieves controlled expansion and sufficient penetration. As a result, the FBI adopted the Glock 19 and 17, chambered in 9mm, in 2016. This reversal reflects the fact that modern 9mm JHP bullets are more effective than they were more than 30 years ago due to the engineering efforts of ammunition manufacturers. 9mm bullets are available in various weights, but the most common are 115, 124, and 147 grains. JHP bullets weighing 115 grains used to be less penetrative, although modern loads have narrowed the gap.

Other Considerations

The .40 S&W and .45 ACP cartridges use heavier bullets with greater frontal surface area, potentially crushing more tissue. However, the damage that a bullet inflicts on the target is only one factor that informs caliber selection. There are other important considerations:


While dry firing is a good way of maintaining proficiency with firearms, it’s no substitute for shooting on a range. As regular range practice is essential if you own or carry a firearm for self-defense, you have to consider the cost of ammunition. 9mm ammunition is generally less expensive than equivalent .40 S&W and .45 ACP, reducing the cost of range practice.


More powerful semi-automatic pistol cartridges, such as the 10mm Auto, .40 S&W, and .357 SIG cause accelerated wear on handguns, reducing the weapon’s service life. You’ll need to replace recoil springs and barrels more frequently, especially if you shoot regularly.

Magazine capacity

Handguns chambered in .40 S&W and .45 ACP tend to have lower magazine capacities than 9mm handguns of the same size. The full-size 9mm Glock 17, for example, has a standard magazine capacity of 17 rounds (+1 in the chamber). The .45-caliber Glock 21, by comparison, holds 13 and the .40-caliber Glock 22 holds 16. Whether a difference of two to four rounds per magazine is important enough to influence your choice is up to you. You can always carry additional magazines in pouches on your gun belt.


.40- and .45-caliber pistols tend to recoil more than 9mm handguns, all else being equal. In a full-size handgun intended for home defense, this may not be a limiting factor. However, in relatively lightweight concealed-carry handguns, these cartridges can be difficult to control. This is especially true in handguns that offer less gripping surface. If you need to fire follow-up shots, you will also recover your sight picture more rapidly with a 9mm handgun. If you’re introducing a beginner to centerfire handguns, a 9mm pistol is usually a good place to start, but don’t assume that a new shooter won’t be able to handle heavier-caliber pistols. Practice is crucial.

Find the Right 9mm Pistol

At IFA Tactical, we sell a variety of 9mm semi-automatic pistols for home defense, concealed carry, duty, and competitive target shooting. If you’d like to find the perfect 9mm pistol for your needs, give us a call at (586) 275-2176. We’d be happy to answer any questions you may have regarding handgun makes and models and how to select the best ammunition for your needs.

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Additional resources

A Review Of The 4 Best 9mm Handguns On The Market

Tips For Choosing The Right 9mm Handgun For Concealed Carry

Law Enforcement Trends: 7 Best 9 Mm Handguns

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