Ditto that. Minor fitting may be necessary and also an adjustment in POA to center your POI.FN cuts all the dove tails the same, so yes, they will fit. POI vs. POA will more than likely be off though.
They will physically fit, but the 9mm front sight is slightly taller than the .45's since the 9mm is flatter trajectory.Do the fnx Tac sights fit the fnx 9 I called FN and they said let them know if it does.