Change Depth Range?

I'm trying to render a gun onto the scene from first person. My character has a shadow and there are shadows in the rest of the world, so I want a way to render the gun so it draws above other objects and doesn't clip through walls, and so it if affected by lighting correctly (rendering with a separate camera ignores the shadows).

Is there a way to do this? Do you use a shader or do you need to modify the code with the GL class? I want to do something like glDepthRange(float, float), which lets you manually set how far into the viewport the object renders (for example, glDepthRange(0,0) makes it render at the near plame, glDepthRange(1,1) renders at the far plane)

Is this possible in Unity? Any help is greatly appreciated