Got the bug to crunch some  numbers this morning and built a little database of the weekly update the TSA Blog does of weapons confiscated during carry-on searches. The top airports are below, for Jan. 1 through Feb. 23 of this year. (A complete list of all confiscations, sortable by each column, is available at our main web site on this page).

During these weeks, 185 guns were confiscated. Of those, about 80% were loaded. Of those loaded, about a third had ammo in the chamber. 

Guns labelled as 9mm and .38 caliber were the most popular (60%), with .22 and .40 caliber making up 25%.