There’s still four days before the chart reporting week closes, but look for Mumford & Sons’ “Babel” to score the largest debut of 2012 next week.

The British group’s sophomore set, released Sept. 25, may sell as much as 600,000 copies  in its opening frame, according to Billboard. That total would handily topple the previous biggest 2012 debut, Justin Bieber’s “Believe,” which sold 374,000.

The sum will also be the largest opening week  for a rock act since AC/DC sold 784,000 with “Black Ice” in 2008.

“Babel’s” predecessor, “Sigh No More,” has sold 2.5 million in the U.S. according to Nielsen SoundScan.

So why is this happening? Although album sales are definitely losing ground to single downloads, there are still certain acts whose fans want to hear their complete body of work as the artist intended for it to be heard. This is usually the case for a rock act, like Radiohead or Coldplay, who is not as dependent on Top 40 radio and pop support as a superstar like Rihanna or Katy Perry. While such artists’ albums sell well, the bulk of their sales has switched over the digital singles sales.  That’s not to say that all the radio play that M&S received so far on “I Will Wait,” which is at No. 2 on Billboard’s Alternative Songs Chart, and the band’s stop at “Saturday Night Live” this week don’t deserve credit as well.

The pop exception (other than Adele) is Taylor Swift. We fully expect "Red," which comes out Oct. 22, to blow past 600,000 in its first week, despite the fact that her singles immediately top iTunes sales chart as soon as they become available and the album's first single, "We Are Never Ever Getting Back Together " has already sold more than 1 million copies in the month since its release.

Read our review of “Babel” here.