If you need to level up any gun or armor before Taken King HERES a good way
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really old loot cave. Also the best way to do this one is to get on a heavy pike from ember caves, come over and get up next to the tree outside this room and rubber band the trigger and point into the room. You have to move every 10 minutes or so to prevent AFK. Doesn't work very well for engrams since that was all patched however it may work well for XP boost