I'm under the impression that settlement supply lines are not as helpful as they first seemed to be. I don't know if I'm simply not doing it right, but I have several supply lines linked directly or indirectly with Sanctuary Hills and yet the connected settlements still don't receive the important materials to make turrets - no circuitry or other specific junk which I know has been deposited into my Sanctuary workbench. For example, Abernathy Farm was the first settlement I connected to Sanctuary, and yet I can't build turrets, only having metal available.
NOTE: I dump all of my junk into Sanctuary's workbench by default.
Any thoughts or suggestions on this? Or has anyone else struggled with this? Thanks!