If you’re not aware, the St. Gabriel society is a non-denominational group seeking to have St. Gabriel recognized by the Vatican as the Patron Saint of Handgunners. I’m not Catholic, so I never really understood the whole “saint” thing, but it would be kind of cool to have a Patron Saint for handgunners.
St. Gabriel Possenti Society honors Jeanne Assam
The closest saint in the currently accepted canon is likely St. Barbara, patron saint of (long list of other people and) artillerymen. Her connection to firearms is somewhat tenuous, as she died before gunpowder had made it to Europe; thunder was involved somehow, I think.