If someone wants to read more about this subject there is a little about Confederate experiments along these lines in Ironclads and Big Guns of the Confederacy: the Journal and Letters of John M. Brooke by George M. Brooke. If I remember correctly the engineer in charge of these efforts fired from a dry tube, which is the only way that makes sense to Mike and I. We believe the range possible was very short, in the area of 30 to 50 feet, but the way those early ironclads fought, that distance could have been sufficient for a hit to occur.
Used copies of that book are available for about $15.00.
Thanks Tim!
Tracy and Mike