a ak47 with gernade launcher
I think you mean kalishnagov.
depending on the gun, there is different challenges for the gun, (10 headshots, etc.)
The easiest gold gun to get is the gold desert eagle, you reach it when you turn to level 55.
The best gun wold have to be the P90 Silenced with USP and RPG, Stopping Power and Extreme Conditioning But you may think different...............
Do mean how do u get the grenade launcher? Cause theres no RPG assault rifle on cod4. If so you need to unlock it by completing that specific guns tasks e.g. kill 100 people with that gun. Once you unlock it go to create a class and select that gun and choose the add-on you want.
cod4 for sure
google and look for cod4 1.7 updater
This would really be an opinion, but it depends on what you are looking for. For example, a .50 cal sniper is good for longrange, or ak47 for a good machine gun.
Id sugggest using either using the desert eagle or use the perk overkill and using an atomatic weopeon.
The best gun that is fully ato and almost no recoil is the AK-74 with silencer and if you use over kill with 50.CAL claymores and iron lungs AK-74 silencer
There's no revolver in CoD4. I presume you ask this because you've played WaW & have unlocked the Magnum. CoD4's version of the Magnum is a Desert Eagle.