Twin-Synchronized-Anit-Aircraft-Auto-Cannons.
I decided my forward deck (on the nose) definately needs some light AA weapons, and so I started building these AC's.
I started with the barrels and several rings in two different diameters

Here you can see the muzzle breaks (without the cuts) and the first set of rings

Since these central rings need a larger diameter, I slipped a second, larger ring over them

Then the rear barrel "root"

More rings on top of the root, and done were the barrels

Then I built the actual gun housing - rather straight forward