JTO,
You are absolutely right about the capability of the Mauser 27mm. It remains an excellent gun, the only issue being the very high cost of ownership due to its unique calibre.
I'd only suggest that as 'old' as the Aden 30 is, its ballistic characteristics are still in the same ballpark as those of the modern GsH-301 - low muzzle velocity, heavy shell. In the 90s, RO offered the RAF and RN an improved Aden 30 round using low drag and Multipurpose (MP) technology, which would have delivered a useful improvement in range and lower dispersion, but no takers.
The Aden 25 programme was an attempt to deliver a much better performance from an existing gun. The gun worked, but the programme was undone by poor attempts at gun/aircraft integration. (The US approach, where the gun designers also design gun mountings, gun pods and ammunition feeds, is, in my experience, much more sound).
The real step change in gun effectiveness, which has gone largely unremarked in the West, is the advent of radars that can deliver very accurate range and range rate at typical gun engagement ranges. This. in turn, leads to much better fire control solutions. Also, modern aircraft computing systems are delivering updates hundreds of times a second instead of twice a second. As the Sea Harrier FA2 showed, these deliver much, much better accuracy and high hit probability, even with lower rates of fire.
Best Regards to those bothering to read this - please tell me when you're bored.
Engines