http://24.wikia.com/wiki/Weapons_used_by_Jack_Bauer

Someone put a lot of time into research of the show. But you have to wonder about their firearm knowledge with statements like….
Quote Originally Posted by Weapons used by Jack Bauer
After Seasons 1 and 2 Jack Bauer upgraded his weapon of choice from the Sig Sauer P228 pistol to the more compressed and powerful Heckler and Koch USP Compact, cartridged in 9mm.