Apart from probably the very early years of the 7.9 mm (I would have to look this up) we Germans have always used steel jackets cladded with gilding. (Being not sure, by cladding I mean the process done in a rolling mill.) We continue to do it with the current 7.62 NATO ammunition (DM111), only a thin tin coating is added on the outside to make up for the fouling definiencies of lead-free primer mixes. (Ammunition purchased abroad, like FN DM41, may have gilding jackets.)
I am not aware of any German scientific/technical discussion of the relative merits of gilding versus steel jackets, which I also would be keen to read. Germany was always short of copper, so the military did not have a real choice. It was even necessary to reduce the gilding cladding from 10 to 5 and 3 percent to save copper.
The military experience in peacetime is that barrels are not worn out by shooting, but by cleaning. My personal experience is that I prefer the risk of a little increased wear by steel jackets to the ensured much bigger copper fouling by gilding jackets (or solid brass bullets).