Even allowing for spikes in gun sales that follow every mass killing in the United States and attendant political debates about gun control, industry executives said the surge seems unprecedented.

In some areas, a buyer walking into a gun store now will have to wait up to a year to buy a military-style assault weapon. The prices of available semiautomatics have doubled as buyers bid up the dwindling supply, and stocks of Glock handguns are also low…

Nationally, there were 2,783,765 background checks last month, an increase of 38 percent over November, according to FBI statistics. That is the single highest month since 1998, the year the FBI launched the program as a requirement of the Brady Handgun Violence Prevention Act. On Dec. 21, the FBI processed 177,170 background checks, a single-day record.