One should first realize that a handgun is not the best tool to bring to a gunfight. True combat arms are rifles and larger weapons. If I knew I was heading to a gunfight, I would much rather show up with a 7.62 caliber M14 battle rifle… or a tank. Handguns are less accurate and generally utilize much weaker energy ammunition then rifles. Only because of the need for concealability, portability, and practicality would I carry a handgun for defense.
Understand, we only carry handguns as a compromise.
Before any other consideration, one needs to decide on what caliber(s) is/are sufficient to carry and trust their life with. Only after deciding firmly on what caliber(s) is/are acceptable, can we move on to the type of handgun to carry. Choosing a handgun caliber requires reflection of what we want our handgun to do; and that is to stop a fight as quickly as possible.
The first thing in considering the best handgun caliber is to forget all you may have heard about “stopping power.” Handgun stopping power is a myth. Unless you’re in a Hollywood movie, handguns just don’t have the power to knock someone off their feet. Remember that for every action there is a reaction; for a handgun bullet to knock someone back, imagine the recoil experienced at the user’s side. Reports of handgun cartridge “stopping power” are irrelevant because no one really knows how much power or force, in and of itself, is required to effectively stop an adversary swiftly.
Handgun calibers stop an adversary in one of two ways: destroying the Central Nervous System (CNS) or by sufficient damage to a vital organ causing blood loss. Penetrating shots to the CNS at the level of the cervical spine (neck) or above, are the only means to reliably cause immediate incapacitation of an adversary. Unfortunately, aiming for the CNS on a moving target is difficult, especially with a handgun. Most folks train for shooting at the center of mass, and hope to place one or more shots into an assailant’s large vital organs to cause rapid blood loss.
It is not the power of the bullet which ends the fight, but where that bullet ends up in the adversary. Simply stated, shot placement is the most critical component to achieving incapacitation. However, shot placement means nothing if bullet lacks the penetrating ability to reach the CNS or vital organs. Bullet penetration is second only to shot placement as a factor in handgun stopping potential; the vital areas must be reached by the bullet with sufficient power to damage or destroy. The FBI’s requirement for 12 inches (30 cm) penetration or greater in calibrated ballistic gelatin is a good measure of an effective round. Most modern handgun calibers will meet the 12” penetration requirement including 5.7mm, 9mm, .357 mag., .40, .357 Sig, and .45 ACP. The need for reliable penetration weeds out intermediate calibers such as .380, .38 special, and .45 Colt.
After shot placement and bullet penetration, one should consider wound size. There seems to be a lot of talk about “temporary cavitation” vs. permanent wound cavity. Temporary cavitation is the effect of a bullet passing through soft tissue and making a temporary stretch cavity in the person. The permanent cavity is the size of the hole the bullet caused. We should not worry too much about temporary cavitation; although rifle calibers are violent enough to cause organs to tear and sustain damage, handguns caliber stretch cavities don’t seem to cause enough effect. Human organs are very resilient and tend to bounce back after being disturbed, it is the permanent wound cavity in which we need to put our faith.
Modern expanding bullets have somewhat evened the playing field when it comes to the permanent wound cavities. Bullet expansion allows, for example, a .45 caliber bullet to make a .7-inch wound cavity and a 9mm to make a half-inch wound. After years of research and engineering, there are many self-defense handgun loads have proven themselves reliable expanding even if the adversary is wearing multiple layers of clothing. Selecting a reliable, and independently tested, expanding bullet means that any modern rounds should fit the bill as far as size goes but does rule out very small calibers, such as .22 and 5.7mm.
If shot placement, penetration, and wound cavity were all to consider, we would only need to carry one-shot handguns for defense. Ammunition capacity is also important; it is very realistic to think that multiple rounds might be necessary. A shooter may miss several shots, and it’s also possible that you may find yourself in a gun battle with multiple adversaries. When considering handgun caliber, the ability to have multiple shots in quick succession should carry some weight. Revolvers are great tools, but to carry more than six rounds for self-defense requires bulky speed loaders and concealability is compromised.
Just as important to consider as capacity, it shootability. What handgun calibers can one shoot accurately and quickly under heavy stress? It does not good to carry large caliber if you are not capable to make quick and accurate follow-up shots with your firearm. Without making a huge debate about shootablity and capacity, lets consider what the FBI concluded after much research: more folks can accurately shoot the 9mm than most other calibers and the 9mm allows for sufficient round capacity.
The .40, .357 Sig, and .45 ACP are good self-defense calibers but we will conclude the 9mm at the “best” self-defense caliber. The 9mm has less felt recoil and allows for greater magazine capacity then those other calibers. The FBI found that felt recoil of .40 and .357 Sig was a significant contributor to missed shots in the field and in training. The .45 ACP requires a generally larger frame pistol and has less capacity then a 9mm.