Here's the
ATF report listing production/sales figures for 2008, broken down by manufacturer and (mostly) by caliber.
The interim report for 2009 is
here. It has the totals, but not broken down by manufacturer.
Of course, sales of used guns won't be included in those reports.
EDIT - Also noticed that those are just *domestic* production/sales figures, so they're not as useful as I first thought.