Shawn:
The book "The Big Guns" by Edwin Olmstead, Wayne E. Stark and Spencer C. Tucker, was published by Museum Restoration Service, Alexandria Bay NY, in 1997. The ISBN of this book is 0-88855-012x. The book has a subtitle of "Civil War Siege, Seacoast and Naval Cannon". It is a companion book to the "Field Artillery of the Civil War" book and will provide you with a plethora of information concerning the large guns. Photographs are provided for nearly all of the guns discussed. You will enjoy the appendixes as they provide lists of orders, gun foundries, founders, inspectors, list of production by manufacturers, foundry numbers, current locations and survivors. Also provided is a revised and more current listing of field artillery that was orginally in the "Field Artillery" book.
The book "Siege Train" edited by Warren Ripley,published for the Charleston Library Society by the University of South Carolina in 1986 with a ISBN of 1-57003-127-4. It will provide information of the tactial employment of large guns in the swamp lands and coastal areas below Charleston SC during 1863 to 1865.

The wide variety of large guns meant that some required longer to reload than others which meant that there is probably no average time for firing of the large guns. Also, please consider that the quality of the training had a direct bearing on the gun crews. You will find a greater variance between the crews and the results in the large coastal guns than you find elsewhere. Finally, I suspect (notice suspect) that large guns in a tactial role against infantry was very poor especially when you consider that many of the coastal forts fell after being assaulted by infantry.

If you have a question or two about a model of large guns, please contact me.
Regards
Ron