Hello,i have not seen this in months,i want to use it so i could get an achivement,i also want to use it on online matchs and offline matchs

As far as I know, you gotta use the weapon in one of the last single-player missions.
You should try doing those.

Hello,i have not seen this in months,i want to use it so i could get an achivement,i also want to use it on online matchs and offline matchs

It occasionally appear in Crazy Crates MP games too. That's where I've used it.

Oh i found out all by myself i just went into Help&Options>Customise>Game Styles>Create New Game Style>Edit ammo for Armageddon weapon>off to play>Achivement earned Armageddon an Award 5G :D

Note:I did this at home so next time when you see Camie8547 he will have the Armageddon an Award!