The grittyness is the build up of drybrushing over the sprayed undercoat, glad you like it. I myself prefer it to blending, I've tried both, and find that overly blended armour, at least when I do it, makes the mini look like its just come off the parade ground, I like to see them looking alittle worn and torn.
Really great work on all the models. I don't know if you meant it, but the shoulder pads got a gritty texture to them, which could either be an accident or a texture that gives them a weathered look. Keep it up.