How Many Rounds Is Enough? Caliber, Capacity and Defensive Gun Uses

It can be hard to choose the caliber of gun with which to arm yourself and how many rounds you might need to stop a deadly threat. While there’s no shortage of opinions on what is the “right” combination for different situations, an analysis of firearms-related studies and data provides some clarity.

Spectrums of Readiness

Handgun caliber and capacity debates aren’t new and will likely always be rife with heated discussion and strong opinions. There are many ways to try to distill these discussions into broad categories. These attempts are aimed at reducing a large amount of information into a few usable generalities. One such attempt can be broken into “any gun is better than no gun” on one end of the spectrum and “pick the optimal caliber and capacity for the largest range of potential threats” on the other.

Such a spectrum is, at least on a subconscious level, based on the perceived likelihood of threats. Additionally, it is restrictive, limiting the lowest and highest ranges of readiness for potential threats. For example, if your lowest end is no gun and the highest end is a full-frame 9mm with multiple 17-round magazines, it tends to illustrate a large difference between various pistols and calibers. However, these differences in handguns are far less pronounced if you include unarmed, untrained and physically unfit as your lowest starting point, then move through trained, physically fit, and armed with a knife and pepper spray, then work your way through handguns, and finally end up on the other end of the spectrum with options such as rifles, shotguns, 30-round magazines and defensive armor.

When addressing how ready you are for any potential threat, these spectrums can be further broken down into these categories:

• Armed: Proficiency and what tools you possess to address a potential threat
• Accessibility: How easily you can access your tools, if needed, in a given situation
• Capacity: Enough rounds available to address a given situation

Examining these factors, the ideal situation would be to be armed with a rifle, at the ready position, and to possess multiple 30-round magazines. But even this could be debated since there are some situations in which other tools and equipment might be more appropriate. The point of these discussions is that we are rarely at the true end of a spectrum, even when we are unarmed or carrying a full-frame pistol with extra magazines.

Defensive Gun Uses

Finding meaningful studies and national data examining non-law enforcement use of force is difficult. In addition, politics, incomplete reporting of non-injurious events to police, and the dangers of relying on self-report data allow room for dissent concerning the results of many published studies. What we are left with are estimates extrapolating smaller data sets to the nation at large or data gathered through self-report surveys. Having acknowledged these limitations, it is worth noting that many research findings that have been accepted by the overall public within the United States have similar issues.

The first question is how often firearms are used defensively each year. A U.S. Department of Justice report from the 1990s reported 29 percent of violent crimes involved a firearm (1.3 million per year).¹ Although data about violence involving firearms is harder to find in the past decade, overall violent crime has generally trended lower since the ‘90s. However, homicides utilizing firearms have increased since 2020.

Our best source of data was a large representational sample (N = 54,000*) from a survey conducted in 2021 (34 percent polled were gun owners) that reported firearms were used defensively 1.67 million times per year.² Comparing either of these estimates to the U.S. population translates to an approximate chance of needing to defend yourself of 0.005 percent (or 1 out of 200). If we’re looking only at gun owners, the percent jumps to 0.015 percent (or 1 out of 66).

According to this same survey, 82 percent of those uses did not involve firing a gun. In other words, just the presence of a firearm halted the potential crime or violence. As a result, the average chance of needing a firearm if you are a firearms owner is 1 in 66, and the chance of needing to defensively fire your weapon is only 1 in 370. Fifty percent of those reporting defensive use faced more than one potential assailant, and 80 percent of encounters occurred at the person’s home or property.

Obviously, these are national estimates and may vary from region to region as well as with individual levels of risk. My personal odds of experiencing violent crime were obviously higher when I lived in a dense urban area (when part of my job was making late-night bank-deposit drops) compared to my situation now: I work from home in a low-crime rural setting. However, these estimates of risk suggest that in the majority of incidents, the event will be at your home and will likely be defused by the mere presence of a gun — any gun.

Caliber and Stops

The defensive use of a firearm can also be broadly defined as one of two forms of ending a threat: a psychological stop or a physiological stop. The psychological stop would include the 82 percent of non-firing uses but would also include when a single round is fired, not necessarily causing a physiological stop but still resulting in an end to the threat. A physiological stop involves needing to fire the weapon until the assailant is unable to physically continue to present a threat.

Similar to defensive usage studies, research of real-world data on the effectiveness of various calibers is often lacking or limited. One of the best original data sets (N = 1,785 shootings) was collected by Greg Ellifritz in 2011.³ He analyzed emergency room data involving gunshot wounds — with caliber information included — spanning a 10-year period. The percentage of fatal single shots varied from 21 percent to 34 percent when comparing .22 Long Rifle up through .44 Magnum.

Similarly, the average number of rounds resulting in a physiological stop varied from 1.38 to 2.45 across all common handgun calibers. This supports the “any gun” hypothesis. However, the trends for percentage of one-shot stops (ranging from 30 to 59 percent) and percentage of failures to obtain a physiological stop (ranging from 9 to 40 percent) generally favored larger calibers, supporting the notion that defensive guns chambered in larger calibers offer certain advantages.

A similar study in 2018 examined four years of criminal actions in Boston (N = 367) that resulted in one or more gunshot wounds with a known caliber.⁴ The study examined three categories of calibers: small (N = 61, .22 LR to .32 ACP), medium (N = 213, .380 ACP to 9mm), and large (N = 93, .357 Magnum to 10mm).** There were no systematic differences between the three categories of calibers across number of wounds or location of wounds resulting in a person being treated by emergency services. However, medium calibers were 2.25 times more likely to result in a fatality and large calibers 4.54 times more likely to result in a fatality compared to smaller calibers. To summarize, the data supports that in many situations, any gun is a viable tool, but in the less-likely-but-more-violent encounters, there is an advantage to larger calibers.

What the Data Reveals

This information is provided to help create a baseline to estimate the number of accurate rounds that may be needed versus the probability of a given event. The data suggests that presenting yourself as a resistant target (presenting determined armed resistance without shooting) or taking one shot (resulting in a psychological stop) were, by the numbers, far more likely to resolve a self-defense incident than needing to achieve a physiological stop (shooting until the threat has stopped).

In the first two scenarios, the type of firearm, caliber and capacity seem to be irrelevant. However, when looking at the need for a physiological stop on one or — as reported 50 percent of the time — more assailants, the advantages of larger calibers and higher capacity are clear. It is better to be overprepared than underprepared. But this strategy should also be balanced with the likelihood of any given scenario. Temper your decisions with an objective acknowledgment of your own fitness and training level as well.

* N = denotes the total number of respondents who completed the survey.

** Large calibers did include one fatal shooting with a 7.62x39mm rifle round in this data set.

Endnotes

(1) Marianne W. Zawitz, “Firearms, Crime and Criminal Justice: Guns Used in Crime,” U.S. Department of Justice, Office of Justice Programs, Bureau of Justice Statistics, July 1995, BJS. OJP.gov/content/pub/pdf/GUIC.PDF.

(2) Jacob Sullum, “The Largest-Ever Survey of American Gun Owners Finds That Defensive Use of Firearms Is Common,” Reason.com, Sept. 9, 2022, Reason.com/2022/09/09/the-largestever-survey-of-american-gun-owners-finds-that-defensive-use-of-firearms-is-common.

(3) Greg Ellifritz, “An Alternate Look at Handgun Stopping Power,” Buckeye Firearms Association, July 8, 2011, BuckeyeFirearms.org/alternate-look-handgun-stopping-power.

(4) Anthony A. Braga and Philip J. Cook, “The Association of Firearm Caliber With Likelihood of Death From Gunshot Injury in Criminal Assaults,” JAMA Network Open 1, no. 3 (July 27, 2018): PubMed.NCBI.NLM.nih.gov/30646040.

The Evolution of Self-Defense Liability Insurance

“Based on some extremely positive survey feedback, we’re about to roll out a new benefit package that will literally blow your socks off,” USCCA Chairman & Co-Founder Tim Schmidt wrote 12 years ago in the May/June 2011 issue of CCM.

Schmidt was alluding to USCCA’s Self-Defense SHIELD, which he revealed in the following issue.

“The USCCA Self-Defense SHIELD is a unique combination of three layers of self-defense protection,” Schmidt explained to readers. “The core layer is an insurance-backed, criminal and civil liability benefit.”

Since 2011, the USCCA has continued to improve this preparation by partnering with a trusted insurance provider. The USCCA purchased a self-defense liability insurance policy that provides the association and its members with insurance. It complements an all-in-one solution that will prepare them for the events before, during and after a self-defense encounter so that they can confidently protect themselves and their loved ones. But USCCA Membership isn’t all about self-defense liability insurance. The USCCA’s premier education and training are what set it apart from its competitors. The USCCA helps responsible gun owners avoid danger, save lives and keep their loved ones safe.

— Frank Jastrzembski, Contributing Editor