From the Crowood Aviation Series book...
View attachment 306506
Geo
I don't know what the sources are for that! At a meeting at the RLM on 19th August 1940 the question of designation for the various versions of the Bf 110 D-0 was raised with an emphasis on designations that could not be garbled in telex messages. A few days later, on the 26th, the following designations were agreed:
D-0: Two external tanks, dackelbauch.
D-2: Two external tanks, either equipped for bombs
or Dackelbauch. Produced by Mtt. Augsburg.
D-3: Two external tanks, equipped only for bombs. Produced by Focke-Wulf, Miag, Gotha.
Unfortunately this was not always the nomenclature used. For example Erprobungsgruppe 210 used the designation D-0/B for what were aircraft identical to the bomb equipped (non-dackelbauch) version of the D-2.
There was a lot of overlap in the designations and resultant confusion. Many aircraft given one designation in the documents of the manufacturer are given a different one in loss reports. It is fair to say that if the Luftwaffe's own record keepers were uncertain at the time, we have little chance today!
To confirm what Denniss has already said, in all the references I have looked at this week-end, I can find NO mention of the cannon armament being removed from any of these sub-types.
Cheers
Steve