This article reviews research undertaken over the past two decades to support international policy on small arms and light weapons (SALW) – which include firearms – and discusses its relevance to academic debates and policy on gun violence. It examines whether SALW research generated a greater understanding of the most problematic uses and users of firearms, and of the role of different weapons as instruments of violence. SALW research helped shift international policy from armed conflicts to gun violence occurring in a range of developing and post-conflict settings, and in Europe following the 2015–16 terror attacks. This work underscored the proximate weapons sources that armed groups often utilise, and the importance of flows of certain weapons – such as converted firearms – and ammunition in fuelling violence. Undertaking impact evaluations of novel interventions, monitoring the impact of new technologies, and investigating the relationship between ammunition supply and violence are suggested ways forward.