An old study, one of questionable validity, shows that firearm availability is correlated with homicide rates. The following is from PubMed.
Firearm availability and homicide rates across 26 high-income countries.
Among developed nations, the United States has the highest rate of civilian gun ownership, and the highest homicide rate. We examine whether the United States is merely an exception, or if a relationship between gun availability and homicide exists across all developed nations.
Homicide rates for the early 1990s come from 26 of 27 of the highly industrialized or high-income countries with greater than 1 million population as classified by the World Bank. Two common proxies for gun availability are used, the percentage of suicides with a firearm, and the”Cook index,” the average of the percentage of suicides with a firearm and the percentage of homicides with a firearm.
In simple regressions (no control variables) across 26 high-income nations, there is a strong and statistically significant association between gun availability and homicide rates.
Across developed countries, where guns are more available, there are more homicides.