if you want to add some scratches without messing with the model or the texturing as it is, if u copy a portion of the faces and apply a texture with a scratch on it an nothing else then position it as close to the original area that you took the section from, that way the original texture is still there underneath and the scratch would be a textured plane over the top. I dont know if what i put makes enough sense but either way it looks really good as is : )
There is on AO there. The reason for too much light in the barrel might rather be the lack of it or the fact that the key light is positioned on a direct line coming from the barrel.
HDR Lighting will definitely help the look and shininess of your model, and likely improve realism - Here’s the tutorial I’ve used.
Blendernerd HDR Lighting Tutorial
Here’s an example of what HDR lighting will do for you on a model I worked on recently.
You should give it a go!!!
