Decades ago, a shooting occurred between a criminal and the FBI. During the incident, a 9mm bullet struck the suspect but stopped just short of his heart. The result was tragic. The attacker continued fighting and went on to kill two FBI agents.
This single event caused a major shift in how law enforcement viewed firearms and ammunition. In the years that followed, many people began to believe that success in self-defence depended on bullet size. Larger calibres, such as the well-known .45 and later the .40, quickly gained popularity.
The 1986 shootout is often cited as proof that the 9mm lacked stopping power. In response, the FBI introduced strict penetration standards for defensive ammunition. These standards soon influenced federal, state, and local law enforcement agencies, and eventually shaped civilian thinking as well. Ammunition manufacturers reacted quickly, redesigning defensive rounds across all calibres to meet the new FBI requirements.
Another powerful influence soon emerged: the digital age. Platforms such as YouTube made testing data, shooting reviews, and performance results widely available. Defensive ammunition was now examined more closely than ever before. Manufacturers could no longer rely on theory alone. Real-world performance, tested and discussed publicly, became essential.
The change from basic full metal jacket rounds to today’s modern defensive ammunition shows just how much progress has been made in a relatively short time.
One clear finding stands out from the data. Penetration performance among high-quality defensive loads is very similar, regardless of calibre or brand. The push to meet FBI standards has created near-equal performance across handgun calibres.
The data also shows that, in real defensive situations, the number of hits needed to stop a threat is largely the same across calibres. On average, it takes two to three hits. This has renewed interest in smaller calibres.
So, what is the real takeaway?
Practice matters far more than calibre.
First, focus on enjoying your shooting. A manageable calibre, such as a 9mm with modern defensive ammunition, often makes more sense than choosing a .40, .45, or 10mm. Reliable defensive rounds are effective, and a controllable firearm makes practice easier and more enjoyable.
Second, let go of the idea of a “one-shot solution”. Choose a firearm based on skill, comfort, and control—not on myths about stopping power.
Finally, true self-defence depends on personal ability. Knowing your firearm and being able to shoot accurately under stress are what matter most.
Regular training is the foundation of this ability. Practice does not have to be limited to live fire. Dry fire training, done correctly, can be extremely effective. Even a few focused minutes several times a week can lead to real improvement.
The evolution of defensive ammunition points to one clear truth: success in self-defence does not depend on calibre choice, but on consistent training. As ammunition technology continues to improve, personal skill remains the most important factor.
If you want to improve your shooting, consider enrolling in our skills building training.