I see no safety reason why a 2" .410 load with 3/8 ounces of shot could not be loaded with about 11 to 11.5 grains of 296. If the sound indicates that the pressure is high enough for good ignition, it sure isn't going to blow up a gun in good condition. Another indication of less than proper ignition would be excessive residue in the bore. Maybe Winchester could give you some confirmation, but I doubt it.