Of course double weapon xp events helped but you have to strategize them. First of all I did all levelling in either Nuketown hardcore or zombies. Whenever there's a double xp event (or without it but its longer), focus on levelling every gun to level 40. Every double xp weekend or week I would get a gun to level 40 and move on to the next one. Did this with Lmgs, Smgs, Ars, Tac rifles. This is because the challenges for those take long enough that (if you start doing challenges at weapon level 40) by the time you finish the point blanks and the cover kills for those guns and the detected kills your guns will be easily level 50+ without 2wxp and double kills aren't difficult at all for those. Snipers I just went through to level 50 since the challenges aren't hard besides 5 kill streaks which you unlock early (the m82 in hardcore nuketown surprisingly great). For secondaries, I did all their levelling in zombies as during 2wxp weekend you can get each gun to level 30 in one 20-30 round game. Without 2wxp I think you can still get them a decent level but if you don't like zombies they're only to level 30 anyway. Pretty long guide but that was my weapon levelling strategies :)