 The LaGG team re-examined the design and pared down the structure as much as possible.Moreover, automatic slats were added to the wings to improve climb and maneuverability on the 35th Series and further weight was saved by installing lighter armament (the first four series were equipped with one axial Berezin machine gun firing through a hollow propeller shaft, two more synchronized cowl mounted Berezin machine guns with 200 rounds per gun and two synchronized ShKAS machine guns above and to the rear of the cowling with 325 rounds per gun; from 8th Series the axial Berezin was replaced by a ShVAK, coupled with a port Berezin in the cowling.But the improvement was slight and, thus, without an alternative powerplant, when the LaGG-3 was first committed to combat in July 1941, it was effective against bombers but it was completely outclassed by the Messerschmitt Bf 109 F.

In combat, the main advantage of the LaGG-3 was the strength of its airframe and the fact that it did not easily catch fire, despite the extensive use of wood.