@Ehliasys
Sorry, forgot your reply.  Yup, I have Octane as well.  Cool program although I never upgraded from the first release as I kept my eyes on Cycles ever since I saw it, and Cycles appears to work the same way as Octane does, so that you get an approximation render while things change and rotate in the scene, and I love that about Octane and Cycles (and hate that about iRay).

@Baggins
Strangest thing, I was just looking at that gun again and the only thing that has changed is the ambient light in my room.  It looks quite alright now, so I assume it's got something to do with the intensity of shadows or occlusion.  The effect has lessened on the gun and increased on the helmet now (I'm being serious, not messing around).

Definitely contrast related, so yup, I'm guessing shadows or occlusion is playing a big part in what I'm seeing sometimes.