The 8"/23 (20.3 cm) Mark 7 was an ASW Howitzer that could be used in place of the standard 4"/50 (10.2 cm) destroyer gun. Besides destroyers, it was planned to mount these on battleships, cruisers and gunboats. Following tests with two British 7.5" Howitzers on USS Caldwell (D-69), the Navy planned to mount two of the new 8" (20.3 cm) Howitzer on destroyers, but none were actually installed. Orders were placed for 89 guns with the first one being test fired in Februay 1918, but it is not certain how many were actually completed. None survived to World War II.

Manufactured from a single alloy-steel forging.

The USN 8"/15 (20.3 cm) Mark 8 was the Vickers 8" (20.3 cm) BL Mark 6 Model 1917 land howitzer that was issued to the US Marine Corps during World War I. Weight with breech block was 6,552 lbs. (2,972 kg).

The data that follows is for the Mark 7 unless otherwise noted.