I know exactly what you mean as I'm an armourer in my day job having worked on ADEN 30mm, 25mm, Mauser 27mm, M134 and many others over the years. I took part in ground firing trials of 25mm at BAe Dunsfold in 1996. As for the gun pods fitted to Harriers these days as you know they are empty and purely there for aerodynamic reasons due to the MoD in its "wisdom" not buying enough sets of under fuselage strakes for the fleet. Those pods in use are the original standard, the type being trialed prior to cancellation of the project were "pregnant" by comparison having had an ammo link collection feature added due the damage being caused to the underside of the aircraft by spent links. By that point in time bar a few minor details the 25mm ADEN was in a pretty good gun. In the end it was problems with the pod that really killed things, ammo feed, gas purging etc. Why an interim 30mm fit was not persued I'll never quite understand but there we go, all history now.
