Rifle weapon material/shader

Hi. Im new in ue4 shader creation, so, have a noob question.

I have textured low-poly model, that look good at 3ds max and Substance Painter.

I connect base color, specular, normal, roughness and ao map and achived this result in game.

How can i achive better results in game? Maybe any tutorials about simple shaders or pbr shading?