I dont understand what you mean by the material not being truly displaced. Are you talking about the normal effecting the shader? Do you also have a copy at hand or a screenshot of the node setup you created? I am rather lost and frustrated with this.
Update I’m looking at this currently.
Hi, could you please reupload the demo file of the handgranade that was posted by Blendtuts at Polycount a while ago? I want to make sure that I understood it correctly but on this mighty fine looking gun I get pretty much close results- given totally different lighting conditions. 
Its on the polycount forum. I thought it would be a good idea to keep it floating around there. Something to note is that his node setup does not factor for the gloss map needing to be inverted it seems.
I’ve been trying to refine my semi-uber shader today, and I’ve gotten it to work correctly for the pistol (no edits, I just plugged in the textures and hit render):
The pipe would most likely require a different shader though, since it’s not using a metalness setup and my shader currently relies on the metalness map to tell it how to color and blend the glossy BRDFs. Honestly, reading through the marmoset docs I still think this is wrong, but I’m not sure how it should be done instead.
simple_pbr.blend (134 KB)
Updated version of the file, contains a no-metalness version of the shader that renders the pipe like this:
simple_pbr.blend (138 KB)
It’s loosely-based on the glossy shader in LuxRender, or should behave fairly similar at least. The roughness is still not quite right, I’m not sure how the roughness mapping is supposed to work. I tried various combos of linear vs sRGB and inverted vs not-inverted and couldn’t get a match.