I'm playing nice "MiG Alley" campaign (still waiting to "bounce" in any american jet, though) and was shocked watching as "Fagot", at that time at top of soviet technology, didn't have yet a gyroscopic gunsight.
And you are activating the gyro mode? I think it defaults to fixed, you have to toggle through to get gyro mode, you have to manually bind the key...assuming that the MiG has it.