Go back to the old movie, "Deadly Weapons". In there you will see Rich Davis do his self test of his armor with a 44 Mag revolver. In the same video they show a guy wearing a heavy outer vest that was what we would call Level 4 nowadays, and shot it with an FAL at a distance of about 8-12 inches. Then they shot it again, with the guy standing on one foot, and it didn't knock him over. Disregard the beginning 20-30 minutes of water jug shooting, but the last half of the movie is great, and dispels many old gun myths.