WASHINGTON » The number of federal background checks for firearm sales declined last month following a surge in gun sales toward the end of the year that’s left many retailers out of stock as Washington considered new gun control measures.

An Associated Press analysis of new FBI data published early today shows the National Instant Criminal Background Check system processed more than 2.78 million checks in December. That was a 12-month peak following an upward trend through last fall. The number fell to 2.48 million in January, still greater than any other month last year.

Firearms sales exploded around the country in the wake of the deadly December shooting spree in Newton, Conn., that left 27 dead, mostly children. The rush to buy guns has left many retailers out of stock.

“You can’t do a background check if a guy doesn’t have a gun to buy,” said Mike Fotia, manager at Duke’s Sport Shop in New Castle, Pa. “There’s nothing to buy.”

Fotia said manufacturers and wholesalers can’t fill orders right now because demand is so high.

The number of background checks does not represent the number of firearms purchased, but gun manufacturers use these statistics to measure the health of the gun industry in the U.S.

The 10 percent drop between December and January comes amid a fierce national debate on gun control after the horrific school shooting in Newtown. The number of background checks dropped 26 percent during the same time period a year earlier. Sales typically decrease in January after the holiday shopping rush is over.

Louisiana, Alabama and Mississippi saw the largest declines in background checks from December to January, by about one-third.