Glas Material?

Hi there,

is it easier to create a nice looking Glas Material in 4.9.1?
Im searching for a Glas Material that is really reflective.
I want that the whole HDR or Level reflects on the Glas which i need for a weapon scope.

At the moment im using the Glas Material from the Blueprint Demo and i played with the Values but it´s still not reflective enough.
Also the Glas from the Starter Content is not really reflective. I just want a mix of 50% opacity and 0% roughness with a touch of darker color in it.

I saw a tutorial where the guy is using a Material Blend and a Material Function but i think in 4.9.1 its a bit different so i cant follow the tutorial complete.

Anybody knows a good Glas Material Tutorial for 4.9.1?