"Many dealers, like Carter's Country, agree to voluntarily do that, however, because they're requested to by ATF agents," he said. "But there's no question that every one of the transactions was lawful. And once the gun leaves the store, it's not the gun store's business anymore. It's the ATF. And they often don't fully utilize the information the dealers provide."
ATF officials say the agency regularly collects information on suspicious buyers from dealers and follows-up on leads, but acknowledged they are ill-equipped with staff to adequately investigate every suspicion of a straw purchaser.
There were roughly 3,600 ATF employees in the firearms division in the 2010 fiscal year that ended September, a number that has held relatively steady since the 1970s.
But officials also say the agency is doing its best with limited resources.
In late January, ATF announced the arrests of 20 suspected straw purchasers in the Phoenix area, which, officials said, disrupted a major gun trafficking operation. "We strongly believe we took down the entire organization from top to bottom that operated out of the Phoenix area," William Newell, ATF special agent in charge, said.
Meanwhile, acting ATF director Melson requested that the Obama administration approve an emergency, one-year rule requiring gun dealers to report multiple sales of long guns with detachable magazines -- such as AK-47s and other assault rifles -- as is required for handguns.
The administration rejected the request last month, facing fierce opposition from the gun lobby and a desire to curb excessive government regulation.
The rule is still under review by the Office of Management and Budget and may ultimately be implemented, but not before a period of public comment and debate.