Here's a WIP in stages of my attempt at making Heresy pattern armour.
I'm making him a little bigger than the regular plastics to try out a different technique.

I've removed the Aquila from an Assault marine torso to get the right look for the torso. I'll be adding cables later.

Next I removed the center skull and replaced it with the circular grill from a spare plastic torso. I've also removed the belt buckle from the front.