Why did he need illegally modified AR-15s? Sharks.

A Louisiana commercial fisherman was sentenced to a year and a day in federal prison recently after pleading guilty to possessing seven AR-15s modified to shoot fully automatic, which is illegal for most U.S. civilians. A machine gun is fully automatic. The 39-year-old shrimp boat captain had an interesting defense: he said he needed the modified guns to fire like machine guns at sharks who attacked his fishing nets. He also possessed two silencers. Not sure why he needed those for the sharks. The court didn’t buy the argument.

As described in American Gun: The True Story of the AR-15, the difference between semiautomatic AR-15s and fully automatic AR-15s -- which can cycle through the ammunition in a magazine much more quickly -- has been ongoing in civilian and military circles.