Back when Mumford & Sons released their debut album, Sigh No More, in February 2010, the folk revival rock disc sold a lowly 4,000 copies and snuck onto the Billboard 200 chart at #116.

What a difference two years makes. With Sigh still hanging around the top 30 a mere 2.5 million copies later, the British band is poised to kill the game on Wednesday when their second full-length, Babel, crashes the boards at #1. Not only is the disc guaranteed to debut at the top, it's also on pace to notch the best first sales week of 2012, possibly doubling the previous high-water mark set by Justin Bieber's Believe (374,000).

According to Billboard, the group could sell as many as 600,000 copies during the tracking week ending Sunday. It will be their first #1 debut and the biggest sales week for a rock band since AC/DC's 2008 albumBlack Ice, which moved 784,000 units in November of that year.

Mumford, who recently performed on "Saturday Night Live,"
 are also on track to record the second-biggest digital sales week ever, with an expected 400,000 or more of its final total coming from online purchases. That would put them just behind Lady Gaga's Born This Way, which shifted 662,000 downloads in its first week thanks to an Amazon.com 99-cent sale during its first two days of release.

The group also expect to score their first #1 debut in their native England, which multi-instrumentalist Ted Dwane told the NME was a big deal for them. "Number Two was the best we got with Sigh No More so it would be amazing," he said. "Obviously no-one's going to wish against a Number One record but I know Green Day and Muse have albums out and they're pretty big hitters. If you told me in the '90s that I'd be in a chart battle with Green Day, I probably would have just laughed at you."