Firearms policy has periodically dominated Canadian politics since the late 1960s. Compared to the United States, however, there is little scholarship on firearms policy to the neighbouring north. Using Canadian firearms policy, Aiming to Explain examines five prominent policy process theories employed during the period from the 1989 Montreal Massacre to the 2012 cancellation of the universal firearms registry. Throughout, B. Timothy Heinmiller and Matthew A. Hennigar present rigorous applications of rational choice institutionalism, social constructivism, the advocacy coalition framework, the multiple streams framework, and punctuated equilibrium. The investigations draw on method-based best practices, while also making use of a wide range of data collection and analysis techniques, including inferential statistics, descriptive statistics, process tracing, congruence analysis, and qualitative content analysis. The goal of Aiming to Explain is not to select a single best theory, but to compare their relative strengths and weaknesses in an effort to direct future research and theoretical development efforts in the study of Canadian public policy.