What is intended purpose/path for creating and using mod type "New Gun"?

Greetings,

A little green to the mod process, but trying to quickly catch on. I wanted to create a mod that had the “New Gun” type, but wasn’t sure what the path/process is for creating a new gun that isn’t extending the functionality of the main types (e.g. pistol, revolver, shotgun, rifle). If it doesn’t extend an existing type, I’m not even sure how to activate it or use it in the game.

Any tips on how to make a new gun without replacing one of the existing ones? I figured it would be ideal to leave the existing ones alone if possible so people could potentially have them in their loadout still.

Thanks in advance for the help!