There are many guns in CoD4 so picking the right one is kinda important :narnar:
http://www.cod4central.com/cod4-stat-overview.php (http://www.cod4central.com/cod4-stat-overview.php)
This site has really detailed guides to every gun and reading it gives you some interesting facts and an insight into strengths/weaknesses of all the guns.
For example; the Ak-47 decreases in power when the Red Dot Sight is attached to it - very weird!!!!!!!!!!!!!!!!!
It tells you the best attachments for how you want to play - either aggresive(charging rooms with a mp5) sneaky(silencers) or defensive(red dot scope!)
The ACOG scope (increased range on ingame gun stats bars) only increases your zoom and is pretty rubbish generally if you read the site.
Also some nice stuff about perks + more tips / tricks!
quick link for sub machine guns : http://www.cod4central.com/cod4-weapons-smgs.php
quick link for assault rifles : http://www.cod4central.com/cod4-weapons-assault-rifles.php