Johann,
thanks for posting the pictures and the information about the different models.
You must be a lucky man to have four of this nice rifles.
A hunting friend of mine has a GK in 5,6x57 in a nearly perfect condition.A heritage from his grandpa. The rifle is excellent made( the steelmagazin is a dream), and it shoots 12mm on 100mtr with 4 shots.
From time to time i reload his ammunition,but its a little bit tricky because off the thickness of the cases.
Good hunting with this beautys.
Swampfox