I'm having trouble with: Third Person Gun Framework

I’m having an issue on where to start with the Framework. I tried some tutorials on youtube but couldn’t really find a good tutorial.

I would like the guns to include stuff like bullet velocity, recoil, hitscan, etc.

Got any suggestions on how to do it/where to start?

*Even if you know an open source/free model that I can easily configure amd change the model,please suggest it.