I just have had blender for a for a long time but have been to scared to use it. Yesterday I decided to try to make a gun with the help of a video. It was going great until i exported it as a FBX it looks great in blender but in the program I exported to it had holes, no texture, and the slide was missing faces. Please respond if you have any ideas as to what is wrong 
You have failed to supply any demo .blend file for us to review so I’ll have to assume you have to knowledge to check the following yourself.
Where you have the ‘holes’ check if you model has flipped face normals
For the texture. What type of material are you using ? Are you using image textures, if so what texture coordinates are you using.
The blend file is attached and as for the texture i am using a custom one and the file is a png.
untitled.blend (560 KB)
Internal faces (remove them)
Duplicate vertices (remove them with selecting al then W / remove Doubles)
Inverted normals (recalculate with selecting all then Ctrl+N)
No image textures included in your blend file. (File / External Data / Pack into blend file)
You are using cycles render materials. These won’t export, you have to use Blender Render materials
I using cycles. So there are duplicate faces?
Then change to Blender Render
So there are duplicate faces?
Did you check the highlighted areas above or try removing doubles. I wouldn’t have mentioned these if they didn’t apply to your model
Tried that export to test
