system
Given the following post, respond as if you're commenting on Reddit:
human
[Back To The future] How did that civilian, 1980s bullet proof vest stop Rifle rounds from an AK-47? 7.62x39 is no slouch of a rifle cartridge.

ALSO: how did the Libyans find Doc at the mall but not at his house?  

what did the Libyans have a spy working at the mall who noticed Doc setting up in the parking lot as he left his JC Penny cover gig?
gpt
The Doc created a time machine out of a DeLorean. In the 30 years he had to prepare, it is not out of the question that he created a bullet proof vest that was able to stop high velocity rifle rounds.