Ah ok, I knew they were given HE for the P-39s didn't know for sure if the Yaks had the same ammo.
Actually the Yak and P39 guns only share the same caliber,two different guns and completely different ammo.
The Yak has the same gun as the IL2,37mm that is,and both HE and AP were available and used.The only thing is the Yaks almost never used the AP rounds,not saying never,just that the Yak's were used for a different purpose and HE was used most commonly.