Is their a way to make and add a completely new item to the game from scratch?
Ideally it would mean the item would act like a regular item. So say I wanted to add a new gun, called like BR-2 it would mean:

• BR-2 in a spawnlist for military crate for say
• BR-2 researchable
• BR-2 icon, maybe animation, model
• etc

So it would act like a item that has been in the game before. If I cannot do this would it be possibly to take an existing item and modify?

Thanks!

No, only modifying existing.

Would I be able to duplicate an item and modify it enough? Say I duplicate the LR and then can I modify the ICON and 3d model and damage etc?

Not really, just customize the look with a skin and potentially the stats of it.

How would I go about duplicating and modifying it? I have decompiled Assemebly-CSharp.dll is their something I can find/use in their?