With JSG in my conical shooter (T/C NewEnglander) I still got terrible groups in hot humid weather with 320 gr Lee R.E.A.L.s.
With T-7, Pyrodex R/S, and Goex fffg or ffg the groups do not change that much.
Sorry, but if 4 different powders keep shooting consistently, and one does not, I'll have to blame the powder!