Doing the math, it works out to 14-15 engrams, which doesn't sound bad until you consider that engrams generally drop every 50 kills and engrams from chests or in opening area of the Grasp of Avarice dungeon, don't seem to count. So your basically looking at farming the 1 public event every 30-60 minutes, farming HVT which have the same spawn rate, or farming approximately 700-750 kills. Not to mention if you open a chest and get a gunsmith engram, it resets your progress for an engram. So if you had 49 kills without an engram drop, open a chest and get a gunsmith engram, then it resets that 49 kill progress back to 0. Given how easy most the other triumphs are, I don't get why this objective is so grindy. Even the Among Friends triumph only requires roughly 13 Playlist strikes.