From John M. Brooke's journal.
Alexander M. Brooke was a lieutenant dismissed from the U.S. Navy on December 6, 1861. On 18 November 1862, John Brooke tested his 7-inch Treble banded gun by firing it across the James River at Tredegar. Lt. DeBree had already placed a target "on the opposite side or rather the foot of the hill on Belle Isle. We fired three bolts at it."
Lt. DeBree estimated the target distance at 750 yards "but to the eye it appeared less."
The first bolt shot weighed 17 pounds and passed above the target and penetrated into the bank. Brooke believed it missed because of an inaccurate distance given him. The other shots better as distance dropped on setting of cannon.
Lt. DeBree helped much with the test and fired at least one shot himself.