Rendering problem with materials and my object

I’m designing a custom model and texture for a gun for Fallout New Vegas and I’m running into a few problems.

My first problem is that when I go into texture paint mode, parts of the mesh are missing, but when I go back into edit mode, they’re all where they should be.

This is odd.

anyone have any ideas please?

Did you try Recalculating Normals? (In Textured Modes backwards normals will appear invisible -I think due to not receiving any light)

ah. I shall try that.

but I’m not sure if thats the case since when I go into texture paint mode, whole faces of the model dissappear