Premises is the following. American pilot's wingman has been shot down, American F4 pilot is rtb after missile engagement. He is still within enemy territory though and is going the straight path into friendly lines.

Mig21 pilot's wingman has been shot down, he is also rtb into north Vietnam, the straight path into friendly lines.

F4 pilot flies into some cloud cover at low altitude. After coming out of the cloud though, he sees a glimpse of co-alt mig21 on his right side, in about 02:30 oclock aspect angle.

F4 is equipped with gunpod.

F4 turns into unwitting mig21. F4 manages to barrel into quite close - but not at good gun range yet- against the mig21, from about 30 degrees angle off tail position

Suddenly, the mig21 seemingly spots the F4 and breaks hard right. The fight is on.

place your bets, who would win in such a case?

a) both are guns only
b) F4 has 4x sidewinder and guns, mig21 has 2x atoll2 (possible loadout?) and guns