No. The entire first week of the game was 2x xp. I was already 6th prestige after the first week, it's pretty easy to prestige in this COD if you rotate between weapons/equipment/scorestreaks.
I agree, completing weapon challenges makes a huge difference to ranking up fast. Hammer the 2x XP weekends and PTFO and youre set. I found the best gametypes for xp were kill confirmed and hardpoint. Also dont get confused between SPM and XP. XP is only viewable in the after action report.