One hell of a rack!

[gunbugs]

The biggest problem with that MG-34 arrangement is the guns are going to run out of ammo pretty quickly. I'm presuming those are the double 100 round capacity drums, so not much ammo per gun, and pretty time consuming to re-attach already filled drums to 12 guns. Quite a noise maker, though.
The U.S. quad mount 50cals typically used a 250 round "tombstone" drum, plus a 50cal cycles about half as fast as an MG-34.