UV mapping Problem

heyho all modellers ( texturers?!)
Im new and i didnt know where to post a question about UV mapping so i just posted it here.

Now the question i got my cannon model and i just lay the texture on it and bla.
But i dont know how to lay the texture on the top of the weels and on the opening of the cannon so there is a black "hole" instead of just gold.

Greetings Elendor