The general design follows several decades of work by Bull with fin-stabilized artillery shells, starting at CARDE and later at Project HARP. In these projects accuracy was not a huge concern, the objective was muzzle velocity, and the test articles were finned darts representing missiles. Yet with the removal of the rifling and the soft-metal driving band on the shell itself, the shell could be designed purely for ballistics, as opposed to having the external constraint of the driving band being located near the balance point of the shell. A system combining some sort of rifling for accuracy without a driving ...

See also:

GC-45 howitzer, GC-45 howitzer - Design History

Read more here: » GC-45 howitzer: Encyclopedia II - GC-45 howitzer - Design History