The Bell P-63 Kingcobra was derived from the P-39 during WWII. Although not adopted by the U.S., it was eagerly embraced by the Soviet Air force.
The Soviets were already using a large number of P-39s, and had no reservations using the much improved P-63.
The P-63 was heavily armed, with a 37mm cannon firign through the propeller hub, and four 0.50 cal machine guns (2 in the nose, 2 in the wings).
With its powerful canon and guns, along with armor protection for the pilot, the Soviets successfully used the P-63 for ground attacks.
This P-63 at Chino was named 'Pretty Polly'.
The Kingcobra made a distinctive sound, very different than the radial engine of the Grummans.
Being a mid-engined plane, it has some handling quirks which made the plane tricky to fly at times. Standard instructions were to bail if the plane ever got into a flat spin.
Here's Pretty Polly after parking for the day.