For those of you who have not got your How The West Was Won achievement, this would be a great time to do so. As Rockstar is giving us something else to celebrate this Independence Day Weekend. 4x Xp. Quadruple Xp. So get out there and get your level 50 rank and get this achievement out of the way. It starts 12:01AM Eastern on Friday July 1st until 11:59PM Eastern on Monday July 4th.
The 4X XP counts across all multiplayer modes. So pick your favorite one and go have fun grinding xp (or not, lol). Yes, this also includes the Undead Nightmare expansions as well.