Here's a description of firing the 37mms from the Soviet Il-2 pilot I. I. Pstygo, commander of the 893rd Attack Regiment. This is taken from the book Ilyushin Il-2 and Il-10 Shturmovik by Yefim Gordon and Sergey Komissarov.
"In my capacity as commander I had to test the machine and get my own impressions of its qualities and armament. I made a flight to the test range and there it became immediately apparent there the precise aiming of the cannon presented a complicated problem. The cannon were mounted in the wings a considerable distance from the fuselage, from the aircaft's axis and consequently from the CG. When firing the recoil was so strong that the plane gave a start in the air. What was worse, after aiming and pressing the fire button I noticed that even the first explosions of shells were not quite simultaneous. The explosions occurred rather close to each other. The second salvo displayed even greater discrepancy in the timing of the explosions. The explosions were occuring at an even greater distance from one another. During the third salvo the aircraft rocked so violently the pilot was thrown about the cockpit from side to side and there was no way of checking this rocking of the aircraft. As a matter of fact only the first two shells hit the target."
Pstygo goes on to say that they learned to fire only very short carefully aimed bursts with the 37mms, but only had time for one or two per diving run.
