8-inch Naval Gun

     Since the retirement of all four battleships with a total of 36 16-inch (406mm) guns, the US Navy is left with small 5-inch (127mm) guns (below) on today's cruisers and destroyers for naval surface fire support.  Despite tacit acknowledgement by Admirals that ships must prepare to fight along coastal areas, procurement funding for naval gunfire remains virtually non-existent.  Although some money is provided for research each year to quiet the Marines and other critics, other Navy programs always take priority when it comes to providing large sums for procurement.

    The US Navy plans to equip it's future destroyers with a non-existent 155mm naval gun that promises a range of 60-100 miles.  This will fail unless the Navy can defy the laws of physics because current 155mm (6.1 inch) guns have a range of less than 30 miles.  Apparently, the Navy thinks it can double this range with rocket-assistance.  However, the rocket propellant needed to reach such ranges and the guidance system leave little room for explosives in the projectile.  The Navy tested a 5-inch (127mm) Extended Range Guided Munition (ERGM) for a decade with poor results.  Its projectile was mostly guidance and rocket propellant, so it had room for only 19 lbs of submuntions at a cost of $50,000 a round.  ERGMs may be useful against a few high-value targets, but are too expensive for general use, their GPS guidance can be jammed, and their warhead is far too small.  As a result, the promised 155mm gun will launch a $100,000 missile that will fail expectations too, so new destroyers will go to sea with the inadequate 5-inch guns that have been in the fleet for decades.   

     The simple solution is for the Navy to modernize the proven Mk-71 8-inch (203mm) gun.  This gun was successfully tested aboard the USS Hull in the 1970s (below).  Although the shock and the weight of the MK-71 strained the Hull, the newer DDG-51 Arleigh Burke class destroyers are twice its size, and new designs  are even larger.  A Navy study determined they can fit a modernized MK-71 on the Burkes, but the Navy shelved this opportunity in favor of a vague concept for a 155mm missile launcher called a gun.


     The MK-71 8-inch gun can deliver the firepower of three 5-inch guns, and much longer ranges are possible by procuring the MK-63 8-inch projectile.  This is an upgraded German "Arrow" projectile from WWII, with a long, pointed nose and a sabot sleeve that achieved a range of 41 miles when fired during the Vietnam conflict.  However, an improved aerodynamic shape called "base bleed" later developed by Dr. Gerald Bull for 175mm projectiles can add a few more miles by reducing drag.  The MK-63 projectile weighed 115 pounds (the average 8-inch HE round weighs 260 pounds) and was used against Viet Cong base camps deep in the interior of the country with good success.  Unfortunately, the Navy did not fully develop the round combination (projectile and powder) and the resulting range error was about 250 yards, which is outside the lethal effect of the round.  By simply determining a better powder match to the projectile, the Navy could have cut that range error down to around 80 yards.  Multiple rounds can reduce this error considerably to meet engagement requirements. 

     This 8-inch projectile provides triple the range of 5-inch guns at considerably less cost than any weapon proposed today.   Naval gunfire is needed to provide FIREPOWER to blast enemy defensive positions.  An MK-71/60 firing twenty 8-inch rounds within one minute can provide far greater firepower at a far lower cost than expensive guided munitions.  This is important because the exact location of the enemy is often unknown, so guns blast suspected locations.  In addition, the Navy can modify and use the Army and Marine stockpile of 8-inch ammunition for M-110 8-inch guns that were recently phased out.  Finally, the variety of 155mm projectiles can be fired over 40 miles from 8-inch guns by using sabots.

     The Navy should incorporate an 8-inch gun into the design of future destroyers and cruisers  and begin procurement of 8-inch guns to backfit on the Arleigh Burke class destroyers. The Navy does not need to research (e.g. delay) this subject, it needs to buy MK71/60 8-inch guns now.  To ensure support, 5-inch and 8-inch replica shells should be placed on display in Pentagon and Congressional corridors so decision makers can see why 260 lb 8-inch rounds can provide 350% more firepower than the small 70 lb 5-inch round. (above)  More details about this gun can be found in two articles published in the US Naval Institute's Proceedings: Nov'92 p.104 and Nov'94 p.94                            

2008 www.G2mil.com