In July 1928 the B-class leader was to have an extended after deck house to provide more accommodations. This however meant that there would be no "Y" gun nor TSDS gear. This design was about £30,000 less than the HMS Codrington, the A-class leader. The design was accepted in October 1928.
In June 1929 it was decided to mount a total of four 4.7" guns, asdic, and echo sounder. These added 23 tons to the overall displacement.
The B class ships were to carry more powerful torpedoes than the A class vessels.
The HMS Bulldog had experimental 60° 4.7" guns on CP XIII mounts. This was proved to not work well.