Not my direct knowledge, but it was rumored that when du Pont stopped making powder on the Brandywine & went to the Moosic, Pennsylvania plant, the few round ball shooters in the 1920's did not like this Moosic powder as well. Also have heard that Moosic's normal production had been blasting powder. I presume that is a different grind.
Ogre showed me his test samples down in the basement, probably in the 1980's. He had an interesting story to tell about GOI powder. The appearance of his samples seemed to confirm it, and it was quite in line with what I knew about corrosion of metals. Odd combination, bear with me. When making black powder, the purity of water used is very important. It is not the taste or odd salts in the water that matter so much, but rather certain bacteria. These bugs live in rivers and definitely in wells, some where there is neither sunlight nor oxygen. Some like to eat sulphur. Incidentally their products of metabolism, i.e. Bug Pee, tend to be very corrosive. Moosic orignally powered the mill by a steam engine, so I've heard, and used the steam condensate for mixing powder. Fine, ideal. But at one point, maybe after the mill blew up around 1970 & du Pont sold it, that GOI/GOEX/Whatever plant began using deep well water. From the hard coal region of Pennsylvania. Them there little well water bugs were used to eating sulphur compounds, & now had the opportunity of being able got to chow down on nice fresh sulphur whilst the powder was being ground. Ogre might tell you what this did to the powder, I don't think it was a good thing. I presume that current GOEX powder is made with bug-free water.
The bug thing is a concern for industries running river water though service water systems (Salem Nuclear plant in New Jersey, Delaware River) or guys leak testing large newly-fabricated steel tanks using river water, maybe Texas or Louisiana. Best drain the tank when finished, lest it drain itself after a couple of months. Was good business for my former employer, selling a 6% molybdenum BugPeeProof alloy.