Class for sling build

I'm making a character who is a ranged attacker specializing in slings, but I'm having trouble figuring out what class to use for them. Gunslinger was my first choice, but many of their feats require you specifically using a gun. Then my mind went to Fighter since they have ranged options, but this character isn't really meant to be in the thick of combat (Plus, the party already has a Fighter). The last option I thought of was Ranger, but this character isn't really much of an outdoorsman. What say you, reddit?