Gun sales are up and inventories are down, according to Douglas County gun store owners. The increase, said the owners, began last fall in anticipation that President Barack Obama would be re-elected. Customers said they were concerned Obama would limit the availability of guns. December came and pistols, revolvers and rifles were purchased as Christmas gifts. Then, sales really soared following the school shooting in Newtown, Conn., on Dec. 14. Nationwide, more than 2.7 million criminal background checks on prospective gun buyers were recorded in December, according to the FBI. The only other month that exceeded the 2 million background …