Tirailleur - Blow up outpost objectives without being detected

Thanks @ElliotLH, 

I tried several more times after the post, then did another cache clear on my Xbox and did it again. Must have just timed perfectly, or I dunno lol; but finally completed the challenge by going up behind throwing one sticky bomb on top of turret near back, and the other on back near exhaust. Placed other 2 as normal on guns, then threw the grenade bundle from further than normal and detonated sticky bombs. Popped up instantly; but thank you for getting back to me on the thread so quickly