How about this alternative.
UF-AC-41 " Velociraptor"
The AS-AC-18 is our most common weapon, but it has sadly become outdated. This new, modern variant is designed so that it can be integrated into any of our current designs that use it. It follows the same design principles as previous iterations of the guns, but thanks to modern technology and materials we have made great progress. Better springs, bolts, timing all allow great performance improvements. Fire rate is increased drastically, up to 800 rounds per minute. Muzzle velocity also increases by 25%-50%. In addition all our ammunition has been carefully re-balanced to ensure that all ammo types can be fired from the same gun without recalibration.
After doing some more research, it seems that the Hispano used some specialized systems to reach the performance it did, which won't easily be revised into your existing gun. Otherwise there's definitely a tradeoff between gun weight and muzzle energy.
Hard: 3
UF-AC-41 Velociraptor: This autocannon is a revision of AC18, with several improvements. The gun is a little more tolerant of different ammo weights and the shells have been modified so that mixed ammo belts are possible. The use of more advanced materials has allowed some parts to become lighter, while a heavier bolt and stronger spring allows a rate of fire of 750 RPM, with a final gun weight of 48kg. In infantry use, it has noticeably more recoil, but this is less of a concern on vehicles.
On an unrelated note NAV PM'ed me to ask if a new heavy machine gun could be retrofitted to replace Sorraias on vehicles for free. Usually yes in the case of ground vehicles, but aircraft are much more sensitive to changes in size and weight of their guns and would probably need to be revised.
We are now in the strategy phase. Last change to submit votes for who the Secret Police should investigate by PM; remember that votes from last turn are not counted and should be re-submitted.