In a Mail Call video, R. Lee Ermey answers a question from Tom of Kansas, who wants to know what the biggest gun in the world is. Ermey says to answer this question you first have to define what you mean by big; for we all know that guns like Big Bertha and Anzio Annie are big, but if you are talking total weight and size of the shell, then they are not the biggest. The Gustav gun created by the Germans, takes the cake on this one with an 80cm barrel. The Germans first used this gun in World War II; it was designed to pulverize French defensive bunkers in the early days of the war.