orchid shale
There are no bags of gunpowder in the game. The short of it, I figured it out, when I realized, I can't even carry 50 gunpowder bags. When you get gunpower, it is shown in a powder horn (up to 40 shots worth). If you have a horn with 20 shots of powder and to find 20 more, the new 20 go into the first horn, which now had 40 shots. So if "bag" meant horn, it would be impossible to even carry 50 "bags". So I tried bringing 50 shots of powder (one horn with 40 and one with 10) to Jean-Luc, or whatever his name was, at that worked.
Please call the the quest goal "50 shots worth of powder" to be clearer.