My understanding is that in the past, Goex hasn't been "refined" as much as it could have been thus leaving both larger and smaller granulations of black powder in the can under a single "label" such as "FFFg" or "FFg" when the powder contained therein was a mixture of larger and smaller granules of powder.
Of course, in the BOTTOM of the powder can, it left a collection of especially finer (smaller) powder granules of Goex... a larger percentage of finer Goex powder than would have been found high up in the can as the can was moved around and the finer powder sifted down in the powder can.
Of course, since you used the very LAST of the powder in the can, it was very likely much finer than regular FFFg Goex which may have accounted for the wide range of hits on the target.
It is my understanding that Hodgdon will refine the Goex black powder they make to a much higher degree than it was formally refined thus causing the new Goex to be more consistent and, thus, more accurate.
However, in the meantime, it appears the Schuetzen black powder is extemely accurate in your rifle. If it were me, I'd stay with the Schuetzen Black Powder... and maybe try another can of Goex after Hodgdon gets the new plant in Alabama or Georgia or where ever the new plant is being built to see if Hodgdon has improve Goex any further.
Meanwhile... make
GOOD smoke...
Strength & Honor...
Ron T.