Project Summary/Abstract This study examines the implementation and impact of Gun Shop Projects (GSPs). GSPs are community-driven suicide prevention partnerships between the firearms community (retailers, ranges, and other businesses) and local public or community health agencies aimed at temporarily reducing access to firearms during times of crisis. Suicide rates have increased by 35% over the last two decades and over half are caused by firearms. An estimated one-third of households has a firearm in the home and firearm access is a key risk for suicide. While we know reducing access to lethal means can be effective in reducing suicide, we must ensure these practices reach the most vulnerable group, firearm owners. GSPs reach this population through partnership with and intentional messaging from the firearms community itself. Although GSPs are widely implemented in the U.S., implementation has occurred without rigorous process or outcome evaluations. The field also lacks an understanding of effective implementation practices of GSPs and clarity on the mechanisms by which GSPs work to impact firearm safety behaviors and suicides involving firearms. This study is designed to address these gaps by (1) identifying the implementation core components of GSPs; (2) examining the mechanisms for firearm safety behavior change; and (3) understanding the impact GSPs may have on suicide outcomes. To address these aims, the study includes three research objectives: (1) conduct an implementation process evaluation to understand variation in model adherence and to identify the GSP implementation core components; (2) Use a one group pre-test post-test design and a before and after intervention quasi-experimental design to evaluate the impact of the Colorado GSP on knowledge, attitudes, beliefs, and behaviors favorable to firearm safety and suicide prevention; and (3) use a difference in differences quasi-experimental design to examine the effects of GSP implementation and duration on suicide in counties. We have convened a multi-disciplinary and community-focused team of experts on population health approaches to firearm injury and violence prevention, including the University of Colorado’s Center for the Study and Prevention of Violence and School of Medicine, the Colorado Department of Public Health and Environment, the National Shooting Sports Foundation, and Colorado firearms community representatives. Study results will advance scientific knowledge on involving the firearms community in suicide prevention efforts as a way to optimize implementation of community-level means reduction and safe storage strategies.