If you noticed that people aren't dying when you're shooting them or your bullets aren't registering, this fix is perfect for you.
To get better hit registration in Call of Duty 4, all it takes is a few commands.
First press the tilde (~) key in-game to open the console.
Type /cl_packetdup and then continue reading.
If you get 70 ping or less to the server you're currently connected to /cl_packetdup 1 will give you the best hit-reg.
If you get over 100, cl_packetdup 2 will.
If you have a really bad connection to the server cl_packetdup 3 will improve your hit registration significantly.
To enter the command just press enter. So you would hit the tilde key, type "/cl_packetdup 1" without the quotation marks, then hit enter.
Next you want to check your rate. Some servers change your rate without you knowing, which can result in random lag spikes and horrible hit registration if they change it to a bad value.
To check your rate, type /rate into the console. It should say something like "rate 25000" underneath. If it says anything different from that, change what you typed into the console to /rate 25000. You'll notice a huge difference in hit registration as well if a server has changed your rate.
The last command is snaps. Lots of people say 30 is the best value for this command and personally I'd agree with them but it really just takes lots of messing around with to find the best value for your connection. To change the snaps value simply type "/snaps x" into the console and hit enter, of course replace x with a number of your choice. Again I would recommend 30 as I can hit people easily even on a bad server with this command set to 30.
I hope I helped someone in this community. I figured this would be the best place to post a tutorial like this.