There are nine front hanger sizes for the K-80 that allow fine tuning of the point of impact of the bottom barrel. The top barrel is braced by the rib so only the bottom barrel will move. A larger hanger size pushes it down, away from the top barrel and a smaller size allows it to come up. The hanger is held in place by a hollow serrated cross pin. The pin size is 1.5mm and it is removed using a 1.4mm pin punch. The hole down the centre of the hollow pin is 1mm and a second punch, 0.9mm diameter is inserted down the centre of the pin to provide support whilst it is driven into place. Pin punches are available for this purpose from any Krieghoff dealer.
There is a second hanger at the front of the forearm. This hanger supports the barrels at this point and is adjustable. The block attached to the top barrel has serrations along its edge that mate with serrations in the hanger itself. A threaded cross pin holds the hanger closed against the serrations. I do recommend that you slacken this screw if making hanger size changes more than one size either side of that fitted. This allows the barrels to adjust along their full length rather than from the forearm forward. Please take note, the threaded cross pin is very easily sheared by over enthusiastic tightening. The screw does not need to be so tight as to clamp the hanger in place as the serrations take care of that. The screw only needs to be tight enough to close the hanger onto the block so that the serrations grip. The end of the pin has a slight hollow that should be punched gently to ensure it does not unscrew with recoil.
To change the hanger, support the barrels flat on a padded surface. Allow room underneath for the cross pin in the front hanger to be driven out. Using the 1.4mm pin punch, drive the pin through. The hanger will probably be quite tight on the barrel and it may not be possible to pull it off over the muzzle with the fingers. If so, drive it off gently using a soft “no-mark” drift. A hard piece of nylon is ideal. If it is especially tight it may be necessary to drive part way and then turn the barrel over to drive from the other side, repeating the process until the hanger leaves the dovetail. Once off, take the hanger you wish to use and slide over the muzzle. The hanger will pass over Krieghoff choke tubes without the need to remove them. Align the hanger dovetail with the dovetail in the hanger block attached to the top barrel and start it onto the slide with the fingers. Tap home with the nylon drift until the front and rear edges of the hanger align perfectly with the block. Insert your 0.9mm pin punch into the serrated hanger pin and start the pin into the hole in the hanger. Tap gently until the pin is all the way through and flush. Remove the pin punch.
Hanger sizes are 1 to 9 and each hanger is half the hanger number in size. Number 1 is 0.5mm, number 2 is 1.0mm and so on. Hangers for fixed choke barrels are a numbered in the same way but are approximately two hanger sizes apart. For example a No.6 fixed choke hanger is roughly equivalent to a No.4 choke tube hanger. This is because choke tube barrels are a larger diameter at the muzzle and so already about two hanger sizes different.
Do not become obsessed with hanger size. You are not shooting a rifle. Each hanger moves the point of impact only a little, an inch or so. You have around 15″ of pattern each side of centre so if you are missing targets, changing the hanger is not going to solve the problem. The purpose of the hanger is to get your pattern as close to centre of aim point as possible but honestly speaking it is not going to make a dramatic difference to your shooting. You may centre more targets but that is about it.