The Buttstock looks like if it was missing the Rubber part. I would darker the Plastic parts a tad more, remember that Black plastic is always black, right now it looks like Sandpapered metal. Edit: heres is an example
Please for the love of god DO NOT ADD TAPE!!! You have a decent design and the start of a decent diffuse texture, don't screw it all up with any of those lazy cliches. There are a few key issues with your texture right now. The main thing is the material definition. Your materials are all the same tone and glossiness. It…