All Oeffag variants were armed with two 8 mm (.315 in) Schwarzlose machine guns.
The Austro-Hungarian B.IIIs retained the D.I engine, and were armed with a Schwarzlose machine gun.
Armament of the type consisted of a free-firing 8 mm (.315 in) Schwarzlose machine gun at the rear for the observer, and at least in some aircraft for the pilot there was also a similar fixed, non-synchronised forward-firing gun in a pod above the top wing.
The operating principle was actually the same as that used in the Model 07/12 Schwarzlose machine gun used by Austria-Hungary during the First World War.