Desperate mesh help needed with nifskope and blender. How to combine 2 different weapons mods meshes together to create one weapon mod?

[1nt5]

Hi guys I really need help. See there is a Scar weapon by Doombased which is awesome, but when u add a scope in weapons bench, it removes the rail (default ironsight). How can I do it so that I put the Scope on that rail as one piece weapon mod (like it should be)? Also rail with reflex sight ofc.

 

I tried in nifskope to move the scope mesh into place so that it is positioned correctly when exported as obj file and in blender importing them both (rail and scope) both so that it looks correct.

What is the next thing I have to do? Or is that all done wrong in the first place?

 

U can see in attachment what I want it to look like.