In order to ensure that forces acting on a breech drive when unlocking the breech and pulling out a cartridge case are reduced or even eliminated, a breech of a weapon system is proposed which is formed at least by one breech carrier and one breech head and the breech carrier supports the breech head. The breech carrier and the breech head can be mechanically separated from one another. This separability is achieved in that a control case which has at least one control cam is inserted in the breech carrier. In addition, the breech head has a control bolt which engages in the control cam of the control case and can be guided in it. This measure ensures that the forces acting upon the recoil of the weapon cannot act on the breech drive.