Sunday, January 13, 2013

Naval Gunfire

Naval gunfire capability has been absent since the last WWII era cruisers and battleships were retired.  The fleet has had only 5" guns to support land operations despite the Marine Corp demands for effective support.  No one, not even the Navy, claims that 5" gunfire is an effective support weapon.  Sure, there may be small targets that a 5" gun can effectively service but naval gunfire lacks any serious punch and has for quite some time.

Supposedly, one of the reasons the Marines allowed the battleships to be retired without raising too much stink is that the Navy promised to develop new guns that were larger than the 5".  However, budgetary pressures and, frankly, ill-considered decisions led to the cancellation of all gun programs before any could reach production.

Only now, with the advent of the Zumwalt's 155 mm AGS has the Navy returned even a bit of gun support to the fleet.  Even so, the 155 mm (6") gun is not really adequate for larger or hardened targets.  In addition, we've discussed the extremely high cost of development and production of the AGS and the fact that it requires a ship to be designed around it much like the Air Force's A-10 Warthog was designed around its gun.  The AGS consumes enormous amounts of internal volume and ships services such as electricity.  The AGS cannot be mounted on other ships in the fleet.  Barring a new class of ship designed for the AGS, the gun will be limited to the three ships of the Zumwalt class which does not exactly constitute a readily available gunfire support capability.

We previously discussed the AGS in detail and concluded with the thought that perhaps the Navy should have looked at the Mk71 8” gun instead.  Let’s look closer at the Mk71.


Mk71 8" Gun - What AGS Should Have Been


 The Mk71 was the result of the Navy’s attempt to mount a major caliber gun on a small (destroyer size) hull.  The gun was developed in the early 1970’s and a full scale prototype was produced, mounted on the Forest Sherman class destroyer USS Hull (DD-945), and test fired at sea in June of 1976.  Both laser guided and unguided projectiles were test fired at ship and shore targets.  The range of the gun was given as around 18 miles.  Before anyone leaps for their keyboard to tell me that the Mk71 caused the Hull's hull to crack from the stresses, read this NavWeaps link carefully.

The gun eventually fell victim to budget cuts and misguided Navy priorities in the late 1970’s.

Interestingly, the Spruance class was designed to accommodate the Mk71 as was the USS Long Beach had she be upgraded as an Aegis cruiser.  Further, studies were conducted that showed that Burke class destroyers could accommodate the Mk71 with some modifications.

The attractiveness of the Mk71 as compared to the AGS is due to

  • Cost – when the Navy committed to the AGS the Mk71 development costs were already long since paid for.  The gun was essentially free and a prototype had already been successfully tested.  Advanced rounds, if desired, would have entailed additional costs just as for the AGS.
  • Explosive Power – the 8” round is so much more effective than a 6”.
  • Shipboard Impact – the AGS, as we’ve discussed has a major impact on ship design and ship utilities.  The Mk71 is a simple gun and easily accommodated.
  • Flexibility – the Mk71 is a general purpose gun capable of engaging both ship and shore targets unlike the AGS which has no anti-ship mode.

For reasons understood only by the Navy, gun support has been a virtually ignored capability for many decades.  This is all the more puzzling given the ready availability of a fully developed and proven technology that would meet the vast majority of gunfire support requirements.  Even now, the Mk71 seems a better choice for future applications than the AGS due to the enormous impact the AGS has on its ship.

5 comments:

  1. I couldn't say it any better.

    The Mk 71 was shelved with the recommissioning of the Iowas in the 1980's. Why it was never brought back and put on some of the Spruances is beyond me. With the VLS we would have a land-attack destroyer twenty years ago!

    Large or medium caliber naval gunfire is not always needed, but it is a useful tool. If you're firing unguided rounds, you can hit targets far and wide from offshore, without sending aircraft or UAVs up first. Since WWII it's been used for harassment and interdiction fire to great effect.

    I know right now the emphasis is on precision fires. Common sense would suggest it would be easier to make a guided 8" versus 155mm or 5". But if volume of fire is needed without as much precision, the 8" wins. Then there is weight of fire: Compare 70 versus 260 pounds for the 5" to 8".

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  2. I'm a bit unsure about big guns.

    I can see the point of matching the fleet and artillery guns, but the biggest in the army now is 155mm (in the UK at least).
    But the list of targets that actually need to be hit with a 16" shell to destroy them must be pretty small.

    Ships should be able to provide gunfire support near the coast, but once the ground forces have landed, they should be able to deal out their own gunfire.

    Even the UKs 4.45" gun has a range of over 20km, thats 10km in shore from a ship 10km out to sea.


    Smaller guns are better for interdiction than big ones.
    Simply for ammunition reasons.
    The 155mm weighs 45kg
    The 16" weighs 850kg - 1200kg

    You can fire 20 of the small rounds for one of the bigger ones.
    If you are firing blind to disrupt enemy movements, number of shots is far more important than individual effect at this level.

    Thats before you even consider that the 16" gun weighs 40 times what the 4.45" weighs.

    Sure, if theres a specific target you need to crack open, bring on the 16" shell.
    But for anything else, well, I suppose its earthquake bombs against cluster munitions

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  3. The problem is TrT the AGS doesnt shoot 155mm shells. There are no shells simply missiles fired out of the gun tubes.

    Also the 16in guns could be fitted with bomblets or other features plus the bigger the gun the deeper your enemies must dig.

    Also with extended range munitions the range could be say 50mi out and still hit with over 250lbs of HE.

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  4. The US Navy introduced a series of shells that were "20% overweight" so the 8" on USS Witchita and later ships could fire 335 pound (152kg) projectiles, to ranges of 30,050 yards or 27,480 meters.

    This was the same innovation that made the 16" AP projectile 2700 pounds instead of 2,240 (1125 instead of 1016 kg).

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  5. JH
    Playing fantasy fleet, I would like the Royal Navy to have a pair of stretched Type 45 cruisers with 8 inch Mk 71, Sylver A70 VLS, 2 x 21" Torps, hangar for 4 Merlins (2 ASW, 2 CSAR). Belated replacements for HMS Tiger & Blake.
    I understand the MK 71 could fire extended range by using a discarding sabot to fire a "smaller" 175 mm shell at higher velocity.

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