18"/48 Mark 1/Mark "A" & 16"/56 Mark 4 Naval Rifle

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The product of an early 1920's effort undertaken by the US Navy to develop a modern 18-inch naval rifle, the 18"/48 Caliber Mark 1 was a single rifle built at the Washington Navy Yard for the purposes of evaluation and munitions testing. Approximately halfway completed in 1922 when the terms of the Washington Naval Limitation Treaty came into effect, the 18" rifle was suddenly outlawed and teh decision was taken to complete the construction of the weapon as an experimental ultra-long 16"/56 caliber gun, thickly lined to permit the firing of a standard 16" shell. Delivered to Dahlgren in 1926 and used for munitions testing beginning in June of 1927 as the 16"/56 Caliber Mark 4 high-velocity test gun, evaluations and live-fire tests continued through the 1930's as part of various weapons testing programs.

Mounting world tensions on the eve of the Second World War and rumors of Japanese Battleships being armed with their own 18" rifles led to renewed interest in the 18" rifle for use in future American Battleships, and with the US' abandonment of the Washington Treaty permitting the legal development of 18" rifles once again, the gun was re-lined to its intended specifications and in 1941, redesignated as a 18"/47 Caliber Mark "A" Naval Rifle and began full-scale proof firing in February of 1942, utilizing a "super heavy" (3,850lb) armor-piercing projectile. Though initial testing proved promising, the days of big-gun Battleships were already numbered and with the official cancellation of the entire Montana Class of Battleships in May of 1942 in favor of Aircraft Carriers the Navy's interest in funding research into the 18" rifle waned. The end of the Second World War brought with it the official cancellation of the 18" program, and the gun was removed from the gun line and is now on display.

www.navweaps.com/Weapons/WNUS_18-48_mk1.htm