In between 1942 and 1943, Yakovlev built the Yak-1M, a prototype that would ultimately lead to the Yak-3, coupled with the VK-105PF2, the latest iteration of the VK-105 engine family, where "P" indicated support for a "motornaya pushka" - an autocannon that fires between the engine banks, through the hollow propeller shaft - mounting. It incorporated a wing of similar design but with smaller surface area (), and had further aerodynamic refinements, like the new placement of the oil radiator, from the chin to the wing roots (one of the visual differences with the Yak-1, -7, -9). A second Yak-1M (originally meant as a "backup") prototype was constructed later that year, differing from the first aircraft in that it had plywood instead of fabric covering of the rear fuselage, mastless radio antenna, reflector gunsight and improved armour and engine cooling.