What happened to the 30mm?
ADEN 30mm was fitted to GR1, 3, FRS1 and F/A2.
ADEN 25mm was being developed for UK GR5/T10, etc. RO/BAe and an engineering development company in the Ascot/Windsor area(?) couldn't get around the gun cradle twisting during gun firing resulting in multiple stoppages and excessive cradle cracking - allegedly.
US system on AV8B - gun in one pod, ammo in the other with an up-and-over feed system through the fuselage - can not be fitted on UK Harriers due to additional UK spec kit being fitted in the cross-feed hole - allegedly.