I tend to use "firearm" more now in general conversation. I will use "weapon" as a broader term when referencing a generic potentially dangerous tool. And don't typically use "gun" unless talking with closer friends or relatives. People have a negative bias toward certain words so I try to avoid triggering those while in general conversation.
A "long gun" is a rifle, a "hand gun" is a pistol or gun. Both are weapons, both are also firearms. When I'm shooting with friends or in a relaxed environment they go by the "friendlier" names. When I OC, I carry a weapon. Weapons have a very specific purpose, that's why I carry one.