See here, which lists "[w]orkers supporting the operation of firearm or ammunition product manufacturers, retailers, importers, distributors, and shooting ranges," but prefaces all the categories (not just the gun-related ones) with:

This list is advisory in nature. It is not, nor should it be considered, a federal directive or standard. Additionally, this advisory list is not intended to be the exclusive list of critical infrastructure sectors, workers, and functions that should continue during the COVID-19 response across all jurisdictions. Individual jurisdictions should add or subtract essential workforce categories based on their own requirements and discretion.

The Free Beacon (Stephen Gutowski) notes that, several days ago, N.J. Attorney General Gurbir Grewal defended including gun stores in the N.J. lockdown by saying,