Effectiveness of Handgun Calibers in Real-World Shootings
Introduction
In debates about handgun stopping power, it’s often argued that bigger calibers are more “lethal” or more likely to stop a threat quickly. To cut through myths, researchers have analyzed documented self-defense and law enforcement shooting incidents (excluding military combat and lab tests) to see how different handgun calibers perform in practice. Key metrics include the average number of shots needed to incapacitate an attacker, one-shot stop percentages (the likelihood a single hit stops the threat), and overall effectiveness (failure-to-stop rates and lethality). The findings show that while caliber matters to some extent, shot placement and the defender’s tactics often outweigh minor caliber differences.
Data Sources and Studies
Several studies and compilations provide insight into caliber effectiveness using real incident data:
- Ellifritz’s 10-Year Study (2011): Trainer and analyst Greg Ellifritz collected details on ~1,800 shootings (law enforcement and civilian self-defense incidents) over a decade. His study recorded for each caliber: the number of people shot, number of hits, how many hits were fatal, average rounds to incapacitation, the percentage of assailants not incapacitated, one-shot stop rate, and more. Unlike earlier research, Ellifritz included all hits (not just single-hit incidents), giving a more realistic view of what it took to stop threats in each case.
- Marshall & Sanow “One-Shot Stop” Data: In the 1980s-90s, Evan Marshall and Ed Sanow analyzed police shooting reports to calculate one-shot stop percentages for various calibers. They famously reported very high one-shot stop rates for powerful rounds (e.g. .357 Magnum >90%) and much lower rates for small calibers. However, their method only counted cases where a single torso hit was delivered – excluding incidents requiring multiple shots. This inflated the stopping percentages by ignoring many failures, and later analyses criticized this approach as statistically flawed.
- FBI and Law Enforcement Perspectives: Law enforcement agencies have long tracked officer-involved shootings. Results tend to show little practical difference between major service calibers (9mm, .40 S&W, .45 ACP, etc.) in terms of stopping determined attackers. The FBI’s own wound ballistics assessments conclude that no handgun round guarantees an instant stop – multiple hits are often needed, and penetration into vital organs is more crucial than caliber alone.
- Caliber and Lethality Study (Braga & Cook 2018): A study of 367 shootings in Boston (2010–2014) examined the relationship between firearm caliber and whether the victim lived or died. The authors found a strong correlation between caliber and fatality rate: victims shot with medium-caliber handguns (like 9mm or .380 ACP) were 2.3× more likely to die than those shot with small calibers (.22, .25, .32). Being shot with a large-caliber handgun (.45 ACP or similar) was associated with a 4.5× higher likelihood of death compared to small-caliber hits.
Comparison of Handgun Calibers (.22 LR to .44 Magnum)
The following table summarizes key effectiveness metrics for common handgun calibers, based on a compilation of nearly 1,800 real shootings (Ellifritz, 2011). The table includes: average number of rounds fired until the threat was incapacitated, one-shot stop percentage, the failure-to-incapacitate rate, and the percentage of hits that were fatal. This data excludes accidental shootings and focuses on defensive or criminal encounters.
| Caliber | Avg. Shots to Incapacitate | One‑Shot Stop % | Failure-to-Stop % | % of Hits Fatal |
|---|---|---|---|---|
| .22 LR | 1.38 | 31% | 31% | 34% |
| .25 ACP | 2.20 | 30% | 35% | 25% |
| .32 (ACP & Long) | 1.52 | 40% | 40% | 21% |
| .380 ACP | 1.76 | 44% | 16% | 29% |
| .38 Special | 1.87 | 39% | 17% | 29% |
| 9mm Luger | 2.45 | 34% | 13% | 24% |
| .357 Magnum / SIG | 1.70 | 44% | 9% | 34% |
| .40 S&W | 2.36 | 45% | 13% | 25% |
| .45 ACP | 2.08 | 39% | 14% | 29% |
| .44 Magnum | 1.71 | 59% | 13% | 26% |
Patterns and Observations
- Common Service Calibers are Surprisingly Similar: For mid- to large handgun calibers (.38 Special, 9mm, .40 S&W, .45 ACP), the performance metrics cluster in a narrow range. They generally require ~2 hits on average to stop a threat, and one-shot stop probabilities hover around 34–45%.
- Low-Caliber Rounds vs. Larger Calibers: Smaller calibers (.22, .25, .32) show higher failure-to-stop rates. For example, .22 LR or .25 ACP often fail to incapacitate a determined attacker.
- Magnum Power – Diminishing Returns: While .357 Magnum and .44 Magnum have strong one-shot stop percentages, recoil and muzzle blast can hinder follow-up shots. Realistically, beyond a certain level, extra handgun power yields diminishing returns in quick incapacitation.
- One-Shot Stop Statistics – Context Matters: A large portion of one-shot stops are psychological; many attackers stop simply from being shot, regardless of wound severity. Against a determined or drugged attacker, multiple hits regardless of caliber may be necessary.
- Average Shots (~Hits) to Stop: Across the board, handguns generally require 2+ hits to neutralize a threat if the aggressor does not retreat after the first shot. Even .44 Magnum often doesn’t produce an instant stop if the shot is poorly placed.
- Overall Incapacitation Success: Most service calibers incapacitated ~85–91% of attackers eventually. Even small calibers eventually stopped the threat in 65–70% of cases, though with a higher failure rate and typically slower incapacitation.
Discussion: Caliber Effectiveness in Context
Real-world shooting statistics suggest that within the range of common defensive handgun calibers, differences in stopping performance are relatively modest. A 9mm vs. a .45 ACP produces roughly similar odds of quickly incapacitating an assailant – especially if neither hits a critical structure. This helps explain why many modern law enforcement agencies have transitioned to 9mm sidearms. No handgun round guarantees a one-shot stop, so shot placement and the number of hits are crucial.
That said, caliber isn’t irrelevant. Larger calibers can help disable an attacker physically (through more tissue damage). But shot placement is still the most critical factor. A .44 Magnum shot to the leg may be less effective than a .380 ACP to the heart. Most defensive experts recommend carrying the largest caliber you can control effectively (accurate, rapid follow-up shots). Extreme handgun power has diminishing returns, while very small calibers risk failing to stop the threat. Overall, no handgun is a “death ray” – multiple shots may be needed.
Key Comparison of Common Service Calibers
| Caliber | One-Shot Stop % (torso/head) | Avg. Shots to Incapacitate | Failure-to-Stop % |
|---|---|---|---|
| .38 Special | 55% | 1.87 | 17% |
| 9mm Luger | 47% | 2.45 | 13% |
| .40 S&W | 52% | 2.36 | 13% |
| .45 ACP | 51% | 2.08 | 14% |
As shown, each caliber stops roughly half of attackers with a single well-placed hit, and typically requires ~2 shots on average to finish the job.
Conclusion
When analyzing real-world self-defense and police shootings (omitting military combat and idealized lab tests), the lethality and stopping effectiveness of handgun rounds from .22 LR up to .44 Magnum can be ranked, but the gaps between calibers are narrower than many expect. Larger calibers (.40, .45, .357, .44) do exhibit higher one-shot stop rates and lower failure rates than small calibers, meaning they are more likely to decisively end a threat with fewer hits.
However, no handgun caliber is infallible; even the best have around a 10–15% chance of failing to incapacitate a determined adversary, and often need multiple hits. Training, shot placement, and sufficient penetration matter more than a few millimeters of bullet diameter. In practical terms, carry a reliable firearm in the largest caliber that you can control under stress, load quality modern ammo, and be mentally prepared to fire multiple shots if necessary.
References
- Greg Ellifritz, “An Alternate Look at Handgun Stopping Power,” Buckeye Firearms Association (2011).
- Evan Marshall & Ed Sanow, Handgun Stopping Power (1992).
- Anthony Braga & Philip J. Cook, Journal of the American Medical Association (2018).
- FBI Training Division, “Handgun Wounding Factors and Effectiveness” (1989).