They drop the bomb right at the start: “Lay back, rock & roll, come inside me,” singer Tim Armstrong caterwauls on “Indestructible.” Even before he invokes Joe Strummer, the spirit of punk-rock past, in the same song, you know this is a great punk record, a great rock record — just a great record. West Coast true believers who loved ska, Brit accents and mohawks, Rancid came from the same Bay Area scene as Green Day but never played punk for laughs. Six albums on, Rancid seem as permanent as uranium.Some punk bands sound savage. Rancid sound happy they found punk rock, which saved them from a life of dead-end jobs and assorted addictions. Drummer Brett Reed, bassist Matt Freedman and guitarist Lars Frederiksen can wail on two-tone ska all night, but here the emphasis is on rave-ups and ringing guitars. What’s striking this time is all the songs about death. “Django” grabs an image from an insanely great spaghetti western of the same name — a man dragging a casket across a barren landscape — and gallops across the same bleak desert, riding a twangy guitar. “Ghost Band” is an exhilarating dream about hearing ghosts playing Rancid songs.Rancid find plenty of ways to bend punk’s rules. For starters, they’ve signed with major label Warner Bros., a real indie no-no. “Roadblock” gloriously transforms a chorus from an ancient New Orleans rhythm-and-blues song; there’s a roller-rink organ here and there, not to mention a great ballad about Armstrong getting arrested in Shanghai for protesting Chinese human-rights abuses.Maybe the song that says the most is “Otherside.” Two pals — an atheist and a believer — agree to disagree. The believer dies, and the atheist hears himself saying, “I’ll see you on the other side.” That’s later: Right now, Indestructible shouts how glad Rancid are to be alive.