Beat mission in co op start to finish no achievement

#1XtremeWRATH360Posted 3/14/2013 7:46:01 PM
Anyone have any ideas as to why it didn't unlock?
We started at the start of Forerunner and went through the whole mission and once we beat it no achievement.
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Juan is........NUMBER 1!
XtremeWRATH-Gamertag
#2Pyronix337Posted 3/15/2013 12:26:23 AM
Are you referring to the achievement Bropocalypse? Were you playing it on a high enough difficulty (has to be on Heroic or harder)?