On rifle/shotgun comination guns, generally:
K/Kugel = select K and the rifle barrel will fire.
S/Schrot = select S and the shot barrel will fire.
However S can also mean Sicher/safe on a sliding safety and K can also mean Klein/small caliber if a rifle with 2 calibers so experiment with snap caps before assuming anything.
The Krieghoff Trumpf Drilling has been remodeled a number of times in it's long production, but Separate Kugelspannung usually means that, if you leave the central rifle selector back, the rifle is not cocked and this makes it safe to use the shotgun barrels. If it is pushed forward, however, the rifle is now cocked and also, when you reload and close the action, it automatically recocks until such time as you push this same rifle selector back. The 1971 manufactured model I know has a separate safety for the shotgun (also on top) which DOES NOT ACT ON THE RIFLE. My guess is, this dual system allows trigger pull weight to be lowered without risk of being jarred off by recoil.
