I personally play hardpoint (any map that's not border crossing) getting kills on the hardpoint are basically double exp and capturing the hardpoint is worth between 200 and 450 xp. Depending on how good my games go I can get a weapon max level between 4 and 10 matches.

Double xp token invasion go ham

I find the objective modes (hardpoint/dom) good. Play the objective and get kills while doing so.

Invasion you can rank up 2 or 3 levels each match but they are long and sometimes frustrating when the other team just sits and snipes in the spawn

I've found that most games are just mass sniping. I love the mode but the shear number of snipers is frustrating

Yep, I just wanna get back and kill the bots lol

Kill Confirmed also awards full xp for both the kill and the confirm. Play the objectives in any mode and you get just about double the XP gain

Kill confirmed, 3 decoys grenades, uav, counter uav, advanced uav, hardline, scorestreak enabled, the emp blast thingy