This analysis examines how various handgun calibers—ranging from .22 LR up to .44 Magnum—perform in real-world shootings, based on data from law enforcement and civilian self-defense incidents. Key metrics include the average number of shots needed to incapacitate an attacker, one-shot stop percentages, and overall failure-to-stop rates. The findings suggest that while larger calibers (.40, .45, .357, .44) often show higher one-shot stop percentages, they do not guarantee an instant stop. Smaller rounds (.22, .25, .32) are significantly less reliable but can still prove lethal.

In practice, caliber choice matters less than shot placement and an individual’s ability to manage recoil. Most handgun calibers require approximately two hits on average to neutralize a threat, and even powerful rounds can fail if the shot is poorly placed. Law enforcement data shows minimal performance gaps among popular service calibers (9mm, .40 S&W, and .45 ACP), underscoring that training, accuracy, and perseverance in a defensive scenario are more crucial than a small difference in bullet diameter.

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