You can't buy this stuff at a U.S. gun store. So where do the cartels get it? According to leaked diplomatic cables, there are three sources.
1. U.S. Defense Department shipments to Latin America, known and tracked by the U.S. State Department as "foreign military sales."
2. Weapons ordered by the Mexican government, tracked by the State Department as "direct commercial sales."
3. Aging, but plentiful arsenals of military weapon stores in Honduras, Guatemala and Nicaragua.
According to State Department documents, in 2009 Mexico bought nearly $177 million worth of American-made weapons, exceeding sales to Iraq and Afghanistan. That number includes $20 million in semi- and fully automatic weapons.
"Most of the M16s were sold legally to the Mexican government and disappeared," Kartchner added.
State Department cables obtained by WikiLeaks confirm that fear. One cable from November 2009 reads, "U.S. law enforcement has fair reason to worry a number of weapons simply disappear... "
Another from June 2009 says, "Rogue elements of the Guatemalan military are selling weapons to narcos."
“These are weapons that have been stockpiled either through U.S. aid programs or currently being shipped there under the guise of military support," said a confidential informant in Arizona who has worked for federal agencies such as the FBI, ATF and DEA.
"The governments and military in those countries realize that the economy is such that they are far better off to push these weapons north and sell them than they are to keep them in their own arsenals and reserves," he said.
Evidence of that is also contained in the Small Arms Survey. The table shows U.S. government sales of rifles, machine guns and handguns in the hundreds of thousands over a five-year period number.
And a GAO report from last year details both foreign military and direct commercial sales of arms from 2005 to 2009.
After looking at a warehouse full of high-powered weapons, allegedly stolen by a corrupt Mexican federal police officer, the informant said it was obvious to him that such weapons did not come from the "mom and pop" gun stores identified by the administration.
Read more: America's Third War: Is the U.S. Arming Mexican Cartels? - FoxNews.com