gun synchronization to fire through propeller arc

[kurlannaiskos]

I did look into it a bit further and the machine guns were apparently for aiming purposes only.
...as you say the tracer rounds.
(I can't imagine the 7.62 would be effective on anything but infantrymen)

the 37 mm cannons were more effective against German Armor ,but the pilots found the effect on the aircraft to be sluggish handling and more effort to pull up after making an attack run.
there was also a problem with asymmetrical recoil causing the pilot more difficulty in aiming.