I seem to have found a good match for myself, combining the Martial Core of "Active Camo" and a sniper rifle at point-blank range without a scope. Basically, I'm invisible while using a sniper rifle as a shotgun.
Here is a link to the original video on YouTube: https://youtu.be/KOHfv-EzFFw
This is Part 3 of a blind playthrough of Black Ops III on the PS4. There may be random pauses in the middle of gameplay, so just a heads up. I'm also not sure how long these videos should be, so they will probably range anywhere from around 30 minutes to an hour. Feedback would be appreciated!
