There is a German/Swiss system called the Millennium Gun (35mm); I guess these larger calibre weapons are being developed to go farther out (beyond the range of the 20mm Phalanx) and can also use smart ammunition.
The competition for the DIVAD Gun was between the GD 35mm and Ford 40mm. As I understand the GD 35mm hit an artillery shell in flight (note that this was 1980), however the 40mm had a proximity round so the scoring took into account the miss distance and how a prox round should react.
Furthermore, GD had some submarine issues, these went away when they did not protest the Ford 40mm selection.