how can i render an object (like a gun in a fps game) on top of everything (like showing it even if i went into a wall) with recieving shadows on it?

I tried making a secondary camera and make it only render the gun and it worked fine but the only problem that the gun dont recieve any shadow and dont cast any shadow too. if there is any way to render the gun on top of everything WITH casting and recieving shadows please help. here is some photos of the situation, with and without the secondary camera: 1.without a secondary camera: (recieves shadows but doesnt render on top of everything)

2.with a secondary camera: (renders on top of everything but doesnt recieve shadows)