How to Change a Map in "Call of Duty 4"by Seth Amery ; Updated September 22, 2017
Unlike its console counterparts, the PC version of "Call of Duty 4" -- originally released in 2007 -- allows you to establish dedicated servers, which follow only your rules. Only on dedicated servers can you change the map in the middle of an online multiplayer match, and this is done by entering a command in the console.
Press the tilde key (~) in the middle of a match.
Type word "map," followed by a space, followed by the name of your map. For example, if you want to change to the Ambush map, type "map ambush."