Surely there was a remarkable difference in performance between La5F and La7. The performance of La5FN and La7 is another thing, prototypes always have peak performances while mass production A/C might lagg behind.
I think (!), that the differentiation kalender mentions (from Barkhorn's units report) was based mainly on stuff like "Red nose" of Guards units etc. Definitely it was not possible for a fighter pilot to differentiate between La5FN and F during a normal fight. La7 is a bit easier because of cooler-inlet-position.
OT: Franek, just as a reminder: Lavochkins are not the only A/C which had problems like this. Think about Me109F's breaking apart, DB605's killing guys like Marseille etc. ENd of OT
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