Re: Kunlun Mountains Collectible issue

Hey dude, that's what I did: 
Acess the Battlelog >>> Campaign >>> Mission 5 
There it will be shown the Collectibles. If appears that you collect all, just replay the mission and the achievement "Full Arsenal" will pop up. 

PS: I did it after I saw the 3 endings. I don't know if it's obligated. 

Hope I helped you. 
Greetings from Brazil