ArtyEngineer - What about modifying Naval MK-71

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Subject: ArtyEngineer - What about modifying Naval MK-71 - 8-inch for Army?
Griffin 8/5/2009 10:45:22 PM

I wasn't sure if you were familiar with the MK-71 8-inch, 55 Cal. gun the navy tested in the 1970's or not. If you are familiar with it, why could this gun not be modified for army/marine use. Yes a new design for the rapid firing gun would be necessary, including a rapid loading ammunition feed system, but... Thanks in advance.

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WarNerd 8/6/2009 5:53:03 AM

Checking some available information shows the gun is about 10% longer and heavier than the 175mm gun. Muzzle velocities are close, but the 8" projectile is 109kg vs. 66kg for the 175mm, so the recoil forces could be 75% greater, so even if you mount it on the M1 tank chassis you will probably need to deploy a spade to handle recoil.

The 175mm gun was mounted on the same chassis as the M109, but had to be mounted in an open, elevation only mount, instead of an enclosed turret, traverse was accomplished by the driver turning the entire vehicle. Indications are that there was no ammunition carried on the vehicle itself.

Given that the HIMARS with GMLRS currently handles most of the missions for such a weapon, there is probably not much demand.

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neutralizer 8/6/2009 8:00:22 AM

Its true that gun of 8" or so lingered on in artillery after WW2, but larger calibres that were a feature if both worls wars disappeared (apart from the short lived US 280mm and Soviet 420mm disigned to fire nucs before miniturausation was mastered). However, now anything above 155mm isn't worth the bother. The thing that has changed is precision guidance. A direct hit by a 155mm is more effective than a nearish miss from a dumb 8". If you want to deliver a big bang get a rocket.

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Griffin 8/18/2009 10:03:52 PM

Isn't this assuming that larger caliber ammunition wouldn't have the same modern capability as lower caliber weapons?

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doggtag 8/19/2009 9:37:29 AM

(neutralizer)
Its true that gun of 8" or so lingered on in artillery after WW2, but larger calibres that were a feature if both worls wars disappeared (apart from the short lived US 280mm and Soviet 420mm disigned to fire nucs before miniturausation was mastered). However, now anything above 155mm isn't worth the bother. The thing that has changed is precision guidance. A direct hit by a 155mm is more effective than a nearish miss from a dumb 8". If you want to deliver a big bang get a rocket.

(Griffin)
Isn't this assuming that larger caliber ammunition wouldn't have the same modern capability as lower caliber weapons?
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Are you implying from a precision munitions perspective?

Or from a "dumb iron" (unguided shells) perspective?

Currently, there are newer-design 155mm artillery shells that are superior in performance (range, dispersion, lethality) than the "old school" M107 standard round.

Certainly it's conceivable that using the same further development would've seen corresponding improvements to larger gun calibers.

It's worth mentioning the the US-pattern M110-series self-propelled artillery (the 8" gun it used, not the fact it was a tracked platform) was a different beast entirely when compared to the newer technology in the ill-fated Iraqi Al Fao 210mm gun system.

The US 8" gun used technology little more advanced than what the US was using going into Viet Nam.

The Al Fao system, even at a caliber increase of barely 1/4 inch (203mm vs 210mm) achieved,

through the use of Bull-inspired specially-designed aerodynamic shells (and propellant) an almost phenomenal increase in range, claiming it could achieve just beyond 57km, compared to the M110 which needed RAP to even 30km.

We're seeing the after-effects of that development now with several nations adopting the newer 52-cal 155mm tubes that, with newer shell designs and propellant families, can comfortably outrange the US-favored 39-caliber 155mm tubes: the 52-cal types can routinely reach 40+km, even to 50km, whereas US types typically only range to 30km without assistance (RAP or base-bleed types).

There have been various developments in shell designs that have improved a given caliber's lethality and danger area.

Denel of South Africa designed a new-pattern fragmetation shell for its LEO 105mm artillery system that demonstrated a larger lethality area than comparable model M107 155mm shells which are still in widespread use.

The capability is actually there that newer technology and design incorporated into a larger gun caliber (8" class) has the potential to increase lethality considerably more (perhaps with newer explosives, a modern 203mm fround could be closer on par of destructive performance to something more like the old WW2-era 240mm/9.45" guns).

If we're talking precision munitions, some here would argue that developing precision munitions for a gun built in considerably fewer numbers than standard 155mm tubes would become prohibitively expensive due to a lower production run than as many as would be consumed by the greater number of 155s in service.

Something to take into effect there, though: how expensive do people really think those big guided rounds for the naval 155mm AGS gun for the Zummwalt destryers are going to cost?

At so few ships with only two guns each, these munitions are going to be considerably more expensive than any guided MLRS rockets or other comparable land attack missiles (more than likely to the point the USN won't even be able to afford to fully stock the DDG1000s' magazines to capacity (something like 600-700 rounds per ship?).

Suggesting super-expensive PGMs developed fore a limited number of 203mm guns isn't being any more or less realistic, and would possibly have benefited if both the USN and land-based forces were using the 203mm gun tubes in some form,

on grounds of that whole multi-service across-platforms commonality issues (the USN's AGS projectiles (LRLAPs) are specific only to the AGS 155mm gun system).

Though I don't know the full reasoning behind the slight increase in caliber of the Al Fao gun to 210mm instead of 203mm (Germans used 210mm in WW2 while many other nations, Allies and Axis alike, used 203mm), it could be possible that even such a slight increase offered considerably more performance from a similar caliber/weight combination.

Accuracies at extended ranges of these latest long-ranged 155mm guns is still contested by many over the older 39-cal

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neutralizer 8/20/2009 6:09:13 AM

There is no military need for calibres larger than 155mm or thereabouts. If you want a direct hit from a large unitary warhead deliver it by missile or air from longer range using precision munitions. If you don't want precision but area effects then 155mm is quite capable, particularly if you are using L15 which has been in service for 30+ years so is hardly new.

The advantage of 155mm as the largest calibre is that the shell weight, around 45kg, is the upper limit for a single person (male or female) to lift, and in some countries that's the law although military forces often have exemptions its considered good policy not to ruin your soldiers' backs by repeatedly lifting overheavy objects.

Large calibre guns belong in the garbage bin of history.

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Griffin 8/24/2009 11:41:07 PM

Thanks for the replies.

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Griffin 8/27/2009 11:53:35 PM

Here is some information readers may find interesting about the Mk71 8-inch (203mm) naval gun and wish to further comment.

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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.

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.

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

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WarNerd 8/28/2009 5:17:03 AM

US Naval Institute's Proceedings: Nov'92 p.104 and Nov'94 p.94

Those are 17 and 15 years ago. If we went back farther we could probably find a similar recommendation for using black powder muzzle loading cannon (they could be built with larger bores and firing pressure than breach loaders at the time).

Things change, time to move on.

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LB Big Guns 8/28/2009 6:28:40 AM

I think the first issue of Proceedings I looked at in the early 1970s had an article about naval gunfire support ship. Frankly I think precision munitions make long range artillery far more cost effective than is appreciated. That said I would not get hung up on whether it's an 8inch gun, 175mm, or 155mm. Someone is going to eventually put in service a new large gun and the utility will then become obvious.

In any case if you want a modern naval gun take a look at the AGS 155/62 for the Zumwalt class. It fired a guided (GPS + INS) round to 109km in 2005. Aboard ship it has a water cooled barrel and supposedly can fire off 300 rounds at an average of 10 rounds a minute. The MK-71 was designed in 1971 and tested in 1975 and does not compare with the AGS. What a modern gun larger than a 155mm can do remains to be seen.

The real issue is actually getting NGS. What the USN should want is a low draft double hulled monitor with some armor protection mounting 2 long range guns of 155 to 203mm that can get in close to shore and not have to be paranoid about the mine threat and indeed act as a support ship, limited, to inshore craft. What they built instead was a cruiser.

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