From The Dark Below, where heavy ammo synths were scarce. Xur forgot to bring them for about 6 weeks and the Gunsmith was price fixing them at 950 glimmer. We could either go to the exclusion zone or find an 'enemy forces move against each other' event in a patrol, then use an encore/showstopper bladedancer to spawn kill waves of enemies. Very fun and efficient. One of the very few uses for bladedancer in PvE, besides an invisible medic.