As an old-timer who fought in the thick of the Vietnam War, lemme tell you, I've been through some wild situations in my day. Hootin' gibbons, the rat-a-tat-tat of machine guns, and that unforgettable whiff of gunpowder. But nothin', and I mean nothin', could've prepped me for the ear-splitting hullabaloo that is Metallica's latest record,…