A USA TODAY review found that the FBI issued more than 4,000 requests last year to retrieve guns from prohibited buyers.

"The FBI’s National Instant Criminal Background Check System (NICS) vets millions of gun purchase transactions every year. But the thousands of gun seizure requests highlight persistent problems in a system where analysts must complete background checks within three days of the proposed purchase. If the background check is not complete within the 72-hour time limit, federal law allows the sale to go forward. ATF agents are asked to take back the guns if the FBI later finds these sales should have been denied," USA TODAY reported.

The article said that it was not clear how many gun seizure requests agents successfully executed last year or how many weapons were  recovered. Since multiple firearms can be purchased in a single transaction, the actual number of guns that should have been banned could be even higher.

In addition, said USA TODAY, the government's success record when it comes to retrieving guns that were improperly purchased has also been mixed. In 2004, for example, the Justice Department's inspector general found that the ATF's retrieval efforts were plagued by staffing shortages, technological inefficiencies and a general lack of urgency that resulted in recovery delays of up to a year.

"ATF agents did not consider most of the prohibited persons who had obtained guns to be dangerous and therefore did not consider it a priority to retrieve the firearm promptly,'' report concluded.

USA TODAY said "A separate inspector general's report last year found marked improvement. Of 125 transactions examined between 2008 and 2014, investigators found that the ATF recovered 116 – or 93% – of the firearms. Of the nine outstanding cases, five buyers could not be located. Two had already re-sold the firearms. One case was turned over to local authorities. And another was not pursued because the agency "did not have the resources to retrieve the firearm."