It's hard to know what to make of Social Distortion's over-30-year-cling to their signature sound. Take their new single, "Machine Gun Blues," from their forthcoming album, Hard Times and Nursery Rhymes: The three-minute '30s gangster parable sounds exactly how you would expect the first single from a new Social Distortion album to sound, and either that prospect gets you pumped or you quit paying attention sometime after you heard "The Story of My Life" on the radio for the quadrillionth time. I could easily devote 200 words to the band's lack of surprises, but the fact that the group has long appealed to disparate punk, rockabilly, country and Western, and old-school rock 'n' roll camps warrants some critical respect. Bandleader Mike Ness and crew hit town this week, making up for a canceled date back in November with a two-night stint at The Marquee. Even rabid fans may have problems telling the new album's tunes from the band's greatest-hits back catalog, but that's nothing to sweat. Social Distortion are a testament to melodic punk's golden rule — if you are going to re-write the same song over and over again, make sure it's one that people love.