The texture shows you do have a gasp of the basic Idea, And I can see your using the same sort of tricks I use, however you need to pay attention to detail.
Just a few points that will quickly improvet he texture.
1) Look at your lighting. Front is a good example were your lighting wrong. Light (for pre shading anyway) should be from the top, Not from a sideways angel. Otherwise the illusion is lost when in game as suddenly the shodows will same back to front.
2) Reptinging the same splat... those schorch marks look nig on identical, they should be more varid, and you should think about how the mark got there. a front shot glanciung the side would leave a long streak to the back...
3) Lights are... LOL.

4) Barrel... should be BLACK inside and just make the whole in the end, dont make a ridge. Best way is to use inner shadow as well as a bevel.
Anyway... start a new thred when you have done a bit more (I assume the black is a work in progress...)
aGorm