SayUncle reports on some misinformation coming out of the ATF courtesy of the Washington Post:

But law enforcement officers on both sides of the border have never seen anything like the flood of guns now surging into Mexico. The increase has been stoked by the cartel war and by the ease of buying high-powered weapons since the U.S. assault weapons ban was not renewed in 2004, William Newell, a special agent in charge of the ATF's Phoenix office, said in an interview.

So apparently the surge of illegals coming in from Mexico are buying semi-automatic high powered machine guns and heading back down to Mexico.