Merkel sidelock over-and-under guns leave many options open. The 12 and 20 calibre receivers can accept combination gun or double rifle barrel assemblies. Interchangeable barrel assemblies can also be installed retroactively. The exclusive features of 313E und 323E correspond to the over-and-under shotgun of this series. Both have a double trigger with articulated trigger. The stock has a pistol grip, a German cheek piece and hogback comb.