As shown in the clip, when on prismatic with Gunpowder Gamble the kinetic weapon kill does not give any stacks as Gunpowder Gamble is supposed to after this season's buff when on solar with Gunpowder Gamble in PvP it will work correctly with non-solar weapons, it does seem to be working as intended even on prismatic in PvE but just specifically non-solar weapons on prismatic in PvP it's not working correctly