The number of FBI background checks required for Americans buying guns set a record in December.
The FBI said it recorded 2.8m background checks during the month, surpassing the mark set in November of 2m checks.
The number was up 49% on December 2011, when the FBI performed a then-record 1.9m checks.
Consumer demand for guns appears to have accounted for the uptick in activity.
There were no changes in FBI background check procedures that would have affected the December numbers, FBI spokesman Stephen Fischer said.
However, December is typically the busiest month of the year for checks, due in part to Christmas gift sales.
The figures do not represent the number of firearms sold, a statistic the government does not track.
They also do not reflect activity between private parties, such as family members or collectors, because federal law requires background checks only for sales from commercial vendors with a federal license.
Someone who passes a background check is eligible to buy multiple firearms.
FBI checks for all of 2012 totalled 19.6m, an annual record and an increase of 19% over 2011.
The FBI system - known as the National Instant Criminal Background Check System (NICS) - "processed transactions following normal established protocols", Mr Fischer said.
The national debate on guns has grown louder since 14 December when Adam Lanza forced his way into Sandy Hook Elementary in Newtown and killed 20 children and six adults before taking his own life in one of the deadliest school shootings in US history.
Lanza also killed his mother, the registered owner of the guns used in the killings, before going to the school.
Interest in guns tends to increase after a mass shooting, as customers fear for personal safety or worry that lawmakers might ban certain firearms.
President Barack Obama has committed to pushing new legislation, possibly including a proposed ban on some semi-automatic weapons, this year.
Separately, students from Sandy Hook Elementary school will return to classes tomorrow in a borrowed building.
Teachers from Newtown have spent the Christmas break readying the new building, which one police official described as "the safest school in America" for the children.
Newtown School Superintendent Janet Robinson said the first day back will be as ordinary as possible, but counsellors and extra police will be present.