fyi
1. A gatling weapon used in a flat trajectory scenario (such as a tank firing on troops) would only be really effective if the barrel could cover a large area in quick movements (i.e. traverse the width of a house at 30 meters in one second). I don't believe the current turrets have that speed.
2. The GAU system is entirely too powerful for an urban scenario. You'd have hundreds of slugs punching through houses/buildings/schools for blocks. If you are that unconcerned with collateral damage, you may as well use air power or artillery.