Firearms caused 116 414 nonfatal injuries and 38 658 deaths in 2016 in the United States.1 After a decline in the 1990s, sustained throughout the 2000s, firearm-related suicide and homicide rates are increasing.1,2 The case-fatality rate ranks among the highest at 30%, ie, 1 in 3 individuals injured by firearms dies.1 It is one of the few such lethal conditions for which there is a single, known, avoidable cause. Moreover, it is the only such lethal condition for which there is a controversial congressional ban on funding. The 1996 ban, known as the Dickey Amendment, does not target research itself but advocacy efforts. Yet it has successfully stifled the funding stream for research.3 It has discouraged scientists from pursuing careers investigating firearm-related issues because of intense controversy, lack of prestige, and academic fatigue. This will compromise the field’s future, as few mentors will feel prepared to encourage or nurture academic development in this area. A domino effect will ensue that we may not have funding to gauge.

Braga and Cook4 present their study of caliber as a determinant of death in firearms assaults, funded by a US Bureau of Justice Assistance grant. It is commendable that the grantor allocated funds to obtain scientific evidence in such a relevant, yet politically charged topic. The researchers used a data set from the files of the police department of Boston, Massachusetts, and enriched it by interviewing investigators and reviewing incident and detective case files and reports from emergency management services and coroners. This research followed up a 1972 study by Zimring, who proposed that “if attacks with different types of firearms have significantly different death rates, this lends important support to the theory that effective weapon controls can influence the homicide rate.”5 Similar to work of Braga and Cook, Zimring’s study suggested that large caliber was a determinant of firearm-related death. Collectively, these results posed the possibility of preventing firearm-related fatalities by modifying access to large-caliber weapons rather than by influencing individual behavior and intentionality.

Although Braga and Cook4 focused their conclusion on caliber as a determinant of death, their investigation illustrated the multifactorial pathogenesis of gun-related deaths. Multiple factors were associated with death and likely modified the effect of other predictors on survival. For example, it is likely that the region of the body wounded, number of wounds, and caliber interacted.

Caliber corresponds to the bullet’s outer diameter and was traditionally reported in inches but has more recently been reported in millimeters, particularly for military weapons. Caliber is a potential factor in determining tissue damage in gun-related trauma, but, contrary to common beliefs, is not the most important.6 The bullet’s capacity to disrupt tissue is best estimated by the kinetic energy (KE = 1/2 mass × velocity2) imparted by the bullet, measured in foot-pounds (ft-lb). Consequently, bullet velocity is much more important than mass. For example, a 0.22-caliber handgun (0.22 in [5.59 mm]) has a caliber similar to the AR-15 assault rifle (0.223 in [5.66 mm]), but the latter has a vastly larger destruction power (a handgun firing a 100-grain bullet at 1000 ft/s yields a KE of 100 ft-lb, whereas an AR-15 firing a 55-grain bullet at 3250 ft/s yields a KE of 1300 ft-lb). Furthermore, high-velocity (>2500 ft/s) bullets produce tissue destruction beyond their direct pathway because of the bullet’s instability on striking tissue, provoking the bullet’s deviation, fragmentation, and sometimes cavitation.6 Even handguns with similar caliber have different damage potential. For example, 0.38-caliber revolvers, used by police in the 1960s and 1970s, produce less KE (220 ft-lb) than the 0.357 magnum (624 ft-lb) because of the propellant amount, despite a larger caliber.6 In fact, the well-known 0.45 Colt has a muzzle energy of only 250 ft-lb. Braga and Cook4 accounted for this variation by classifying the rifle-related homicide (caliber, 0.30 in [7.62 mm]) as large caliber even though its actual caliber (0.30) is smaller than most weapons classified as medium caliber. The bullet mass, propellant, jacket, and other characteristics of the bullets also play significant roles in wounding potential.

The distance between a gun and its target influences survival, as the bullet’s KE decreases with distance traveled after firing. Indeed, the increased odds of death in indoor vs outdoor shootings in Braga and Cook’s study is in line with the likely longer distance traveled by bullets in outdoor shootings. Also shown in the study, the number of wounds (“rounds on target”) is associated with survival. However, number of wounds is not independent from caliber, as small-caliber weapons may allow more bullets to be shot with precision (ie, “on target”) and within a shorter period. This underscores the deadly nature of assault rifles, especially the civilian version of the AR-15 used in several mass shootings in 2017 and 2018, which can carry large-capacity magazines that permit shooting 30 or more bullets without reloading.7 Indeed, increases in number and severity of wounds have been implicated in the upward trend in the case-fatality rates of gunshot wounds in recent years.8 In addition, human tissues vary in how easily they are damaged by bullets.

Several data sources are needed to understand the complexity of circumstances involved in firearm injuries. Ideally, police reports should be merged with clinical data sets. Notwithstanding the difficulties for such an undertaking posed by patient confidentiality, some of the existing clinical data sets suffer from low quality. Indeed, Thiels et al9 showed that clinical data missingness was much greater in firearm incidents compared with other injuries in the National Trauma Data Bank, a national repository of trauma-related hospital data. Lack of personnel prepared to gather information in the sensitive circumstances surrounding gun-related episodes is likely a major culprit.

The lack of information, low-quality data, and the difficulties in merging data sets from different sources (police, legal, behavioral, medical, coroner, etc), compounded by scarce funding and public controversy, demoralize scientists who could provide evidence to inform policy and increase public awareness. Jay Dickey, the House representative who proposed the Dickey Amendment, reversed his position on gun-related research following the mass shooting in Aurora, Colorado, in 2012. In an eloquent 2012 Washington Post editorial (written in partnership with Mark Rosenberg, former director of the Centers for Disease Control and Prevention’s National Center for Injury Prevention and Control, who opposed the amendment in 1996), Dickey called for research funding for firearm death prevention: “The same evidence-based approach that is saving millions of lives from motor-vehicle crashes, as well as from smoking, cancer and HIV/AIDS, can help reduce the toll of deaths and injuries from gun violence.”10

Guns do not kill people; neither do cigarettes, cars, motorcycles, fast food, alcohol, drugs, or sweetened beverages. In contrast to guns, however, our society strongly supports research in preventing the adverse effects linked to these other risk factors. Moreover, we endorse rigorous enforcement of evidence-based medical counseling, required warnings, safety devices, tax increases, age limits, and strict regulations to diminish their damage. We, as a society, must encourage and support scientists, such as Braga, Cook, and others, who, despite the lack of resources, remain dedicated to those affected by the increasing power of firearms.

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Published: July 27, 2018. doi:10.1001/jamanetworkopen.2018.0845

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2018 Sauaia A et al. JAMA Network Open.

Corresponding Author: Angela Sauaia, MD, PhD, 1880 S Xenia Ct, Denver, CO 80231 (angela.sauaia@ucdenver.edu).

Conflict of Interest Disclosures: Dr Moore reported grants from Haemonetics, Instrumental Laboratory, and Prytime during the conduct of the study. No other disclosures were reported.