Fahnenschmied, I looked at your old posts and believe it was post 47 or 48 in which you showed a couple of leather slings. Also, a link on how to make one. At any rate there are paintings depicting slings on Jaegers. They are not intended to be used as a shooting support. They are intended for carrying the rifle. I have been in contact with Kerry Beyers, she sent a photo of one she had made.
I am still researching this and will prototype one out of hemp strap that I have, so I can determine the exact length and configuration that I want.
Needless to say, the military muskets the Germanics employed are more in the line of what the other European powers employed.
It seems that civilian slings had no metal buckles or such, in order to not harm the wood on their rifles. Plus, they were not intended for the rigors of war.