So the gun is emptied in about 7 seconds.
The Su-34 is armed with a 30mm GSh-301 gun and 180 rounds of ammunition. The gun has a maximum rate of fire of 1,500 rounds per minute and the muzzle velocity is 860m/sec.
So the gun is emptied in about 7 seconds.==
The gun shot by computer not pilot. The target laser measures the distance to target then the board computer calculate the firing solution and just fire few shots to hit teh target.
The pilot is just choosing targets by target marks on his helmet.
That's fairly typical of modern fighter cannon loadouts. F-15E, comparable to the Ground attack Su-34, has 500 rounds, but rate of fire is about 6,000 rpm, so the F-15's M61 Vulcan 20 mm cannon is empty in about 5 seconds. (The 20 mm projectiles are much lighter than the 30 mm ones). The A-10s GAU-8, a 30 mm but firing longer and heavier rounds than the Russian cannon, carries 1174 rounds and fires them at around 4,000 rpm. However if do it all in one 17.6 second burst, you'll likely burn out barrels. It's supposed to fire max of 2 second burst with 1 minute between bursts. Of course the ammo drum is the size of a Volkswagon Beetle. :)