Ok if you want to be able to use any weapon with all the unlocks in Dedicated servers please watch the following video and do as it instructs.
http://www.youtube.com/watch?feature=player_detailpage&v=JHEaweO2Nko
Just as in MW2 you can change certain things in the Config_MP.cfg file to help. To find this file you need to go to the following location on your computer..... for most of you it will be C:\Program Files (x86)\Steam\steamapps\common\call of duty modern warfare 3\players2
Open the file with notepad or wordpad to edit it.
The first two settings have to do with making your ping more user friendly
seta cg_ScoresPing_Interval "100"
This setting tells MW3 what each bar on the ping scale is worth. I suggest you change it to 25 from 100.
seta cg_ScoresPing_MaxBars "4"
This changes how many bars appear in the ping section. I suggest 8 instead of 4. If these two settings are set correctly then there will be a total of 8 bars. Each bar is worth a total of 25MS. So, if you are in a server and you are missing two bars then your ping is roughly 50MS to the server.
seta drawLagometer "0"
This brings up the famous Lag-O-Meter. I have tested this with a setting of 1 which produced no results. I am going to try 2 and I will update the post if it works.
There are more settings that can be changed. However, I have been unable to test them as of this post. I am going to test these tonight and will let you guys know what settings help and can be changed.
