Estimates for Arms Traffic

The ATF says that 300,000 arms go from the United States to Mexico on a yearly basis. Jorge Castañeda referred in his recent article to the lack of credibility of the "oft-quoted claim" that 2,000 assault rifles slipped over the border every day. I'm not sure how often that claim is made (I wouldn't say it is rote by any measure), but this stat from the ATF would indicate that he's right, and a mere 800 weapons travel from the US to Mexico on a daily basis. Not that this should make us sleep all that much better.