A breech device for bolt-action firearms includes a breech body reciprocating in the receiver and rotatable into locking position. In its front part, the breech body has locking lugs located in three sectors, the locking lugs in at least two sectors being formed in a breech device equipped with a magazine loaded in parallel so that there are four guide surfaces to limit rotation between the receiver and the breech body, and the breech body has a recessed locking surface for the cartridge at its end. The locking surface of the cartridge has been extended downwardly to form a glide surface passing between the locking lugs so that the rear surface of the cartridge case slides on the glide surface and the locking surface into locking position as the cartridge is ejected from the magazine into the cartridge housing.