Data Source: Bureau of Justice Statistics: Homicide Trends in the United States, Homicides by weapon type, & Homicide Trends in United Sates, Figure 42. Homicides by Weapon type, 1980-2008; Bureau of Alcohol, . (Graph: Prison Policy Initiative, 2012)
This graph originally appeared in Supply-side murder control?.
The historical trend is quite clear: handgun homicides track gun manufacturing.