As I recall Nash Buckingham's Fox HE Bo Whoop achieved its nickname from the way it sounded across a Duck Marsh.
Several of my early Lefevers are overbored more like a gauge than by .005". That is a 12 is bored to approximately 11 gauge or around .750". I suspect it was intended for use with brass shells, thus oversized wads. do not know that of itself would cause a change in the sound.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra