Creating a gun with diverse features might be a bit challenging for you, especially if you didn’t attempt creating a gun yet. So start off making a simple gun (like a Glock or even a blaster) - learning the fundamentals and basics of creating a gun. Then you could progress yourself building more complex guns like (rifles, snipers, sci-fi guns) If you have enough knowledge, you could even add features that others couldn’t think of!
In case if you’re lost, check out the resource below. AlvinBlox makes great tutorials about building and scripting for beginners.