Panic in Year Zero! (1962)

Panic in Year Zero! (1962), directed by Ray Milland.

On the first morning of their vacation a family notices strange flashes of light and then a mushroom cloud in the direction of Los Angeles. Yes, it's the Big One, world wide.

Dad (Ray Milland) soon shifts into rather ruthless survival mode, clearing out a grocery before the townspeople know what's up, robbing a hardware store at gunpoint and slugging a gas station attendant. He's not a savage, but family comes first and he's doing what everyone has to when civil society fails.

He spends a lot of time arguing with his wife (Jean Hagen) but the son (Frankie Avalon) is having a good time: carrying and using guns, crashing through road blocks. It's all matter-of-fact and realistic, the things you have to do at the end of the world as we know it: get supplies and guns, find a place away from other people, don't trust anyone. Perform executions as necessary.

The state of nature is particularly hard on the women: the daughter is raped and they later rescue a young woman kept as a sex slave after her family was murdered. Dad showed mercy to some thugs earlier and that turns out to have been a mistake.

The low budget production values don't hurt this at all, but there are problems:

On the same two-sided disc with The Last Man on Earth (1964).