BAE Systems 155-mm Advanced Gun System - Lite (AGS-L)

[Triton]

Model of BAE Systems 155-mm Advanced Gun System - Lite (AGS-L) on display at Navy League Air Sea Space Exposition 2013.

Source:

PDF of sale brochure for BAE Systems AGS-L:

http://events.us.baesystems.com/SAS/prodserv/pdf/BAE-Systems-AGS-LITE.pdf

 

[TomS]

Interesting that BAE are still referring to the seemingly mythical unguided 155mm ASuW Projectile. They've been talking about it for years, but there's no sign they've actually developed it.

 

[RP1]

Unguided? I remember an RO paper from 2001 with a sub-munitions-dispensing ASuW 155mm projectile?


RP1

 

[Sea Skimmer]

Interesting that BAE are still referring to the seemingly mythical unguided 155mm ASuW Projectile. They've been talking about it for years, but there's no sign they've actually developed it.

It was formally cancelled as a requirement by the USN, 2005 or so I think, past that its just notional from the company. This was also around the time when DD(X) was shrunk down to DDG-1000 and they were looking to among other things reduce magazine space for cost reasons. They also dropped the requirement to fire the Army Excalibur guided shell for shorter ranged precision missions.


Frankly it isn't a great loss, in view of how rarely naval gunfire is ever used it may well be cheaper or at least no vast cost increase to fire large numbers of GPS guided rounds in wartime, while saving the expenditure of large numbers of unguided shells in regular training over the forty year lifepsan of the ship (think we'll shoot unguided shells in 2050?). They are cheap but they aren't free either. The effective ban on new DPICM rounds, and coming deadline to phase out existing ones already considerably undermined the value of small numbers of unguided 155mm rounds from a warship, and in the early part of the new century it became pretty clear that the Congressionally mandated 1% or less dud rate could not be met which is when LRLAP itself lost its cluster warhead. At least not as long as unarmed duds were counted the same as armed duds or without some radical breakthrough in fusing technology.

 

[TomS]

Unguided? I remember an RO paper from 2001 with a sub-munitions-dispensing ASuW 155mm projectile?

The brochure says "When engaging surface targets, the AGS-L system will be capable of firing a high-capacity ballistic 155-mm ASuW projectile (ASuWP)" [Emphasis mine.]
In naval rounds, "high capacity" usually means unitary, but that's not certain (there was a High Capacity Artillery Projectile in the late 1990s/early 2000s that was a submunition dispenser). But unguided (ballistic) seems to be definite.

 

[Grey Havoc]

Frankly it isn't a great loss, in view of how rarely naval gunfire is ever used it may well be cheaper or at least no vast cost increase to fire large numbers of GPS guided rounds in wartime, while saving the expenditure of large numbers of unguided shells in regular training over the forty year lifespan of the ship (think we'll shoot unguided shells in 2050?). They are cheap but they aren't free either. The effective ban on new DPICM rounds, and coming deadline to phase out existing ones already considerably undermined the value of small numbers of unguided 155mm rounds from a warship, and in the early part of the new century it became pretty clear that the Congressionally mandated 1% or less dud rate could not be met which is when LRLAP itself lost its cluster warhead. At least not as long as unarmed duds were counted the same as armed duds or without some radical breakthrough in fusing technology.

Problem is, when GPS is taken down or otherwise compromised. I agree with you that not developing new cluster munitions and phasing out existing ones is idiotic in the extreme.

 

[Sea Skimmer]

If GPS is down the shells will still be vastly more accurate with INS guidance only then a purely unguided shell. The GMLRS program for example originally expected to get 30m accuracy with INS only, back when the plan was for a large portion of the missiles were not even going to have GPS at all for cost reasons. Unguided rounds will come down hundreds of meters away at long range, say 40km as is typical for modern 155mm calibers, without lengthy corrections. This can make it impossible to fire a mission at all particularly if the mission is high angle with troops closely engaged as it often must be in mountain/jungle/urban fighting that gets so much attention today.

http://www.dtic.mil/ndia/2012armaments/Tuesday14034weyer.pdf

In the above BAE specified that AGS-L fitted on a DDG-51 hull would have 180 rounds of ammunition fired at 5-6rpm. With unguided ammo that really doesn't get you very far at all. DDG-1000 has several times as much ammunition, but its still only about as much as a 155mm SPH battery would have in the field.


Guided shells also have a major advantage for firing MRSI missions, as you can exploit the guidance to warp the flight paths in ways that would otherwise be impossible. This is very handy for a naval gun which has a fixed powder charge, unlike a howitzer on land. MRSI really improves the effective firepower of only one or two naval guns firing, thus reducing the amount of ammunition actually needed for a mission. Or at least most sorts of missions, obviously it won't help if you need a long protective barrage. The powder charge issue was a side problem, while unguided shells exist for 155mm in the inventory, new cased powder charges would have been needed to fire it from AGS. That means spending actual money for designing and testing them.


I think the main place unguided ammo would be missed is illumination and smoke, but nobody was ever proposing to give AGS these sorts of rounds nor do the types that exist in the US inventory have very long range even by the standards of the US's unimpressive 155mm land howitzers.

 

[Void]

Is this a mockup of the ASuWP perhaps?

 

[sferrin]

That round 2nd from the right looks interesting. Almost like it's got a booster on it.

 

[Abraham Gubler]

That round 2nd from the right looks interesting. Almost like it's got a booster on it.

That's a Gerarld Bull designed Extended Range Full Bore (ERFB) type shell.

 

[Void]

What is unusual though is the length. It is visibly longer than the 1.5m long 5 inch Standard Guided Projectile (2nd and 3rd from the left).

Denel's 155mm ERFB shells are only about 850mm long. The mystery shell looks about twice their length.

Here is where I found it:

https://flic.kr/p/bMZ77T

View: http://www.flickr.com/photos/baesystemsinc/7083951967/

 

[Abraham Gubler]

What is unusual though is the length. It is visibly longer than the 1.5m long 5 inch Standard Guided Projectile (2nd and 3rd from the left).

Denel's 155mm ERFB shells are only about 850mm long. The mystery shell looks about twice their length.

Well clearly it isn’t an existing ERFB shell which is why I said an ERFB type shell. The length to breadth ratio of the legacy ERFB is based on the best aerodynamics for its particular velocity which is attuned to the L45-52 cannons that launch it. This longer ERFB shell could be designed for a higher velocity shell like one would expect from the higher pressure chamber, longer barrel of the AGS

 

[Bhurki]

Why is the AGS (155mm) so much heavier than the mark 45? (104t vs 21t respectively)
Even the Mk71 (203mm) was only 78t.

 

[TomS]

Why is the AGS (155mm) so much heavier than the mark 45? (104t vs 21t respectively)
Even the Mk71 (203mm) was only 78t.

So, AGS had a muzzle energy around twice that of a Mk45 firing ERGM. It also had about twice the nominal [Edit] sustained rate of fire as a Mk 45 firing ERGM (double cycling to load round and propellant). That led to the inclusion of active cooling for the barrel. The combination of relatively fast autoloading, heavy recoil, and active cooling all drives up weight. The weight probably also includes the stealth gunhouse where the barrel stows. And it may include some part of the magazine, since that was to be fully automated and it's not exactly obvious where mount stops and magazine begins.

Ccompared to the Mk71, AGS was a bit less powerful and slightly slower, but had active cooling and a much more elaborate loading system. That plus the stealth gun house probably explain the differences there.

 

[TomS]

Details of the proposed installation on a DDG-51 Flight III

 

[Scott Kenny]

Is this a mockup of the ASuWP perhaps?

I assume that the super long shell is the LRLAP? And the shell on the (edit) far right is the "standard" BAE GPS-guided 155mm shell?

 

[that_person]

This isn't exactly AGS-L, but there was apparently consideration to putting 2 full-size AGS mounts on the San Antonio-class LPD hull instead of building Zumwalts. This idea was floated around 2006, and first debuted in a Defense News article I have been unable to locate. It was then talked about in a 2006 CBO document linked here: https://apps.dtic.mil/sti/tr/pdf/ADA448137.pdf Option 5 for the Navy's 313-ship plan envisioned building 5 such ships. There where similar designs under consideration during the 1980s too.

 

[Scott Kenny]

Gotta admit, I have always wondered why the 'phibs never had any significant shore bombardment capabilities designed in...

Early Phibs had some 5" guns that were more for self defense than shore bombardment, which basically got removed in the 1990s. But only 6x guns in single turrets.

 

[that_person]

Gotta admit, I have always wondered why the 'phibs never had any significant shore bombardment capabilities designed in...

Early Phibs had some 5" guns that were more for self defense than shore bombardment, which basically got removed in the 1990s. But only 6x guns in single turrets.

Once helicopters joined the fleet, it became apparent that we could keep the amphibs well off shore. There was no reason to risk running into a minefield for a land-based ASM battery.

It should be noted though that the Tarawas where designed with 5” guns, there was consideration to put ABRS on the Newport LSTs, and the San Antonios where designed with 16 VLS cells, presumably for ESSM and TLAMs.

 

[Scott Kenny]

Once helicopters joined the fleet, it became apparent that we could keep the amphibs well off shore. There was no reason to risk running into a minefield for a land-based ASM battery.

Excellent point. And kinda what killed the EFV planing-hull amtrack. Cheap coastal defenses got more range quickly enough that even a 30+kt amtrack couldn't get the big 'phibs out of range.

It should be noted though that the Tarawas where designed with 5” guns, there was consideration to put ABRS on the Newport LSTs, and the San Antonios where designed with 16 VLS cells, presumably for ESSM and TLAMs.

I'm not so sure about TLAMs on the San Antonios, but I'd believe ESSM and SM2 (assuming that the Tonis have radar capable of illuminating for them, or that there's finally an SM2 active homing version).

 

[Yellow Palace]

Excellent point. And kinda what killed the EFV planing-hull amtrack. Cheap coastal defenses got more range quickly enough that even a 30+kt amtrack couldn't get the big 'phibs out of range.


I'm not so sure about TLAMs on the San Antonios, but I'd believe ESSM and SM2 (assuming that the Tonis have radar capable of illuminating for them, or that there's finally an SM2 active homing version).

The design logic supposedly went something like:

• If an LPD full of Marines gets sunk, it'll be a PR disaster that probably leads to losing the war.
• The new LPD should have full self-protection to combatant standards.
• Holy crap, putting a guided missile system on an LPD really drives the cost up. Maybe we shouldn't bother....

By that point, the VLS space had been designed in, and rearranging the ship to remove it would have been unduly expensive. So it just got repurposed - IIRC, as usually happens for weird spaces in odd places, as a gym.

 

[Firefinder]

Needs to be pointed out that the Navy considers it still possible to install the Mk41s.

A plan to do so pops up like twice a decade and thrn dies cause of budget.

 

[Winchester]

Excellent point. And kinda what killed the EFV planing-hull amtrack. Cheap coastal defenses got more range quickly enough that even a 30+kt amtrack couldn't get the big 'phibs out of range.


I'm not so sure about TLAMs on the San Antonios, but I'd believe ESSM and SM2 (assuming that the Tonis have radar capable of illuminating for them, or that there's finally an SM2 active homing version).

SM2 would have been a non-starter - you'd have to stick a frigate-grade fire control system (SPY-1F and SPG-62) on there to guide it.

ESSM would have required some form of illuminator, but the SPS-48E radar already installed was plenty.

Tomahawk on the other hand is just the launcher and some consoles, no additional topside electronics except maybe some datalinks.

Also, it should be mentioned that the Navy has spent most of the last decade trying to figure out how to integrate some form of long range strike capability on the LPD-17s using methods other than installing the VLS, after that was deemed impossible to do. Like chaining missile launcher trucks to the deck and launching from there. No one's been talking about better air defenses for the ship since the early 2000s.

 

[MadRat]

I dont know about no one talking about better air defenses. The need for intercepting missile swarms and hypersonic missiles has been pretty well pumped. Drone swarms should also be a future priority.

And some people seem to suggest ESSM is limited to semi-active radar homing. Thats a new one as the shooter is only required to be linked to the CEC thats been rolled out and only getting better. With its mid-course command link it seems like a natural to 'evolve' into a land targetable version. Whatever would make ESSM able to do that would probably be applicable to future versions of NASAMS. Come to think about it, a sea-based NASAMS might be a good alternative to an AGS-L, if the IIR of AIM-9X and bi-mode seeker of AMRAAM-ER could offer precision strike modes. May not have the incredible distance of AGS, but time of flight is only a fraction.

 

[Scott Kenny]

SM2 would have been a non-starter - you'd have to stick a frigate-grade fire control system (SPY-1F and SPG-62) on there to guide it.

ESSM would have required some form of illuminator, but the SPS-48E radar already installed was plenty.

What FCS would you need for the vertical launched ESSMs, though?

Because if that FCS is also capable of playing nice with SM2...

Also, why isn't there an SM2 active radar homing missile. Yes, there's SM6 but that's optimized for extreme range work. I meant something with SM2 range and either Patriot-style TVM or active radar homing. As many missiles as we've produced, the cost per missile should be pretty trivial.

Tomahawk on the other hand is just the launcher and some consoles, no additional topside electronics except maybe some datalinks.

True enough, but it's wasting an enormous amount of the range available. The US needs a 300 mile range cruise missile with a huge warhead to drop into those cells.

 

[Yellow Palace]

Also, why isn't there an SM2 active radar homing missile. Yes, there's SM6 but that's optimized for extreme range work. I meant something with SM2 range and either Patriot-style TVM or active radar homing. As many missiles as we've produced, the cost per missile should be pretty trivial.

Block IIIC is supposed to bring active homing to the medium-range Standard. I'm not sure why it took until 2017 to approve development; it was in trials last year, whether it's actually been deployed yet I'm not sure.

 

[that_person]

From what I understand, ARH missiles are more expensive, heavier, and can’t differentiate a CH-53 from a ASM. That probably isn’t a good thing for a amphib fleet. I assume we’re only doing ARH missiles now because of those risks.

 

[Winchester]

What FCS would you need for the vertical launched ESSMs, though?

Because if that FCS is also capable of playing nice with SM2...

Also, why isn't there an SM2 active radar homing missile. Yes, there's SM6 but that's optimized for extreme range work. I meant something with SM2 range and either Patriot-style TVM or active radar homing. As many missiles as we've produced, the cost per missile should be pretty trivial.

You're not getting a useful amount of SM-2 in a 16-cell launcher, so even if the fire control system did play nice, it's not the greatest idea to put SM-2 in cells you could be using for ESSM or Tomahawk, both of which are more immediately useful or can be taken in higher quantities. ESSM can also use much less powerful fire control systems since they don't need to have the same range as an SM-2.

Seriously, you can guide ESSM successfully with something like SAAB Ceros or STIR 1.2 or even the funky things they use on the carriers that I don't remember the designation for; Standard requires a substantially bigger director (SPG-51, SPG-62, STIR 1.8) or something like APAR or SPY-3 which are basically X-band multifunction units that can both do air search and illuminate targets for SM-2 at the same time.

As for the lack of ARH missiles, for a very, very long time, no one really wanted active radar seekers on surface to air missiles because of the risk of an oops if the missiles were launched. If you launch a semi-active missile like SM-2 and discover that it's going towards the wrong target, you can turn the illuminator off and it will forget where it's going and dive into the ocean. If you launch an active missile and its seeker turns on, you have no further control over where that missile is going, so you had best be extremely positive about what you're shooting at and that there's nothing in the general direction the missile went that you care about.

(It's basically the same problem that led to TASM being retired - absolutely no control over where the things would go once it went active, which could be several hundred kilometers away. About the only place that was useful was if you're launching it up the inlets to Murmansk and Polyarnyy where anything sunk would be a hostile by default. Modern fire-and-forget missiles have imaging seekers that let them recognize targets before engaging, which makes it less of a problem).

 

[Scott Kenny]

You're not getting a useful amount of SM-2 in a 16-cell launcher, so even if the fire control system did play nice, it's not the greatest idea to put SM-2 in cells you could be using for ESSM or Tomahawk, both of which are more immediately useful or can be taken in higher quantities. ESSM can also use much less powerful fire control systems since they don't need to have the same range as an SM-2.

8x-12x SM2 and 16x-32x ESSM is nothing to sneer at. (Probably 12x SM2 and 16x ESSM, though 10x SM2 and 24x ESSM may be a better loadout)

My issue with Tomahawks in that specific VLS is wasting ~1200mi worth of range. Though I suppose the Block IV version where the sensors on the TacTom and datalink can act as a drone for ~3hrs isn't a complete waste, but still. I'd rather launch a Mojave off the flight deck for that job.

 

[Voltzz]

I m not 100% sure this is for the AGS, but the shell looks way too long for anything else:
BAE Bofors DARAAS (Deep Attack Rocket Assisted Artillery Shell)

 

[Scott Kenny]

I m not 100% sure this is for the AGS, but the shell looks way too long for anything else:
BAE Bofors DARAAS (Deep Attack Rocket Assisted Artillery Shell)

I was not expecting a staged rocket out of a 155mm gun...

 

[that_person]

One thing I'd like to point out about the LRLAP. Had a sizable number of shells been produced, the unit cost would be significantly lower than the cited $800,000 - $1,000,000.

This 2001 article is saying less than $50,000 per shell

https://www.nationaldefensemagazine...-can-they-deliver-affordable-precision-strike

This was then echoed again in 2002 when United Defense presented a unit cost of $30,000 - $50,000

Department of Defense Appropriations for 2002

books.google.com

Citation 5a from NavWeaps gives me the impression that some sort of agreement was reached for $35,000 per round, albeit it was optimistic:
"In July 2004, Terry Bowman, Lockheed Martin business development spokesman, was projecting that the LRLAP round would have "a cost of $35,000 per round. It will definitely be a challenge." As the forecasted cost of the 5" (12.7 cm) ERGM round is at least $50,000, it would seem to be unlikely that the much larger LRLAP round would be so significantly less expensive."

USA 155 mm/62 (6.1") Mark 51 Advanced Gun System (AGS) - NavWeaps

www.navweaps.com

Mr. Bowman's statement seemed to have come true, as a 2007 Masters Thesis from an Army Colonel quoted LRLAP at $75,000 per shell. The citation he listed is no longer available though.

https://www.defenseindustrydaily.com/files/2007-05_JFSC_Thesis_NFS_and_DDG-1000.pdf (edited)

It was only after we had cut down orders down to 150 total shells that the unit cost spiked

https://www.secnav.navy.mil/fmc/fmb/Documents/17pres/PANMC_1_BOOK.pdf

Now here's my question. I keep finding references to other types of AGS ammunition, an enlarged ERGM, a standard 155mm ballistic round, and a SADARM round. Navweaps called the ballistic round the "Ballistic Long Range Projectile", and even has stats for it, but there is nothing online about it. The other ammo types I can only find vague mentions in passing, although CBO documents keep saying "family of munitions", so clearly other ammo types where planend.


That's from Polmar in 2001(?). Does anyone have further info on the other shell types?

 

[Scott Kenny]

One thing I'd like to point out about the LRLAP. Had a sizable number of shells been produced, the unit cost would be significantly lower than the cited $800,000 - $1,000,000.

Also, note how much M982 Excalibur ammunition prices dropped, from $260k each in 2015 to $68k one year later as production greatly increased.

Does anyone have further info on the other shell types?

Not really.

Obviously, the AGS was optimized around shore bombardment, so the expected ammunition types are going to be HE, DPICM, and SADARM, possibly with a bunker buster shell in the mix if the basic HE can't do the job.

Not sure why you'd need an ERGM unless the Zumwalts were planning on staying 50ish miles out to sea and you were shelling targets over 50nmi inland. ERGMs tend to swap explosive payload for rocket booster. As points of comparison, the M795 155mm shell has a 9.12kg explosive fill, while the rocket boosted M549 has a ~7kg explosive fill. The LRLAP as standard has an 11kg explosive fill.

 

[TomS]

Also, note how much M982 Excalibur ammunition prices dropped, from $260k each in 2015 to $68k one year later as production greatly increased.


Not really.

Obviously, the AGS was optimized around shore bombardment, so the expected ammunition types are going to be HE, DPICM, and SADARM, possibly with a bunker buster shell in the mix if the basic HE can't do the job.

Not sure why you'd need an ERGM unless the Zumwalts were planning on staying 50ish miles out to sea and you were shelling targets over 50nmi inland. ERGMs tend to swap explosive payload for rocket booster. As points of comparison, the M795 155mm shell has a 9.12kg explosive fill, while the rocket boosted M549 has a ~7kg explosive fill. The LRLAP as standard has an 11kg explosive fill.

There is some terminology confusion there. ERGM (Extended-range guided munition) was at one point a generic term -- the 155mm LRLAP was a sort of ERGM. But then the term ERGM became specifically associated with the 127mm round.

The Navy was planning to keep the Zumwalts well off shore. It all feeds back into the USMC requirement, which was to perform counterbattery fire against Soviet/Russian 130mm artillery firing at inland helicopter landing spots, while keeping the firing shop at least 25nm offshore. That led to an objective NGFS requirement for a range of 93nm, which is what LRLAP was supposed to achieve. The threshold was 63nm, which is what the 127mm ERGM was designed for.

 

[Scott Kenny]

There is some terminology confusion there. ERGM (Extended-range guided munition) was at one point a generic term -- the 155mm LRLAP was a sort of ERGM. But then the term ERGM became specifically associated with the 127mm round.

I was assuming that a mention of ERGM as a variation of LRLAP was some flavor of extra-boosted range, like how conventional 155mm has HE, Base Bleed, and Rocket Assisted for different ranges.

The Navy was planning to keep the Zumwalts well off shore. It all feeds back into the USMC requirement, which was to perform counterbattery fire against Soviet/Russian 130mm artillery firing at inland helicopter landing spots, while keeping the firing shop at least 25nm offshore. That led to an objective NGFS requirement for a range of 93nm, which is what LRLAP was supposed to achieve. The threshold was 63nm, which is what the 127mm ERGM was designed for.

Ah, okay, that makes more sense now. I don't remember having ever heard/read that requirement.

 

[Kat Tsun]

There is some terminology confusion there. ERGM (Extended-range guided munition) was at one point a generic term -- the 155mm LRLAP was a sort of ERGM. But then the term ERGM became specifically associated with the 127mm round.

The Navy was planning to keep the Zumwalts well off shore. It all feeds back into the USMC requirement, which was to perform counterbattery fire against Soviet/Russian 130mm artillery firing at inland helicopter landing spots, while keeping the firing shop at least 25nm offshore. That led to an objective NGFS requirement for a range of 93nm, which is what LRLAP was supposed to achieve. The threshold was 63nm, which is what the 127mm ERGM was designed for.

The Marine NGFS expectation was built with the A-222 in mind? Very strong energy. I guess the threshold requirement is for a 25 nmi helicopter landing with H-46 and objective is 50 nmi using V-22s.

I was assuming that a mention of ERGM as a variation of LRLAP was some flavor of extra-boosted range, like how conventional 155mm has HE, Base Bleed, and Rocket Assisted for different ranges.



Ah, okay, that makes more sense now. I don't remember having ever heard/read that requirement.

It's alluded to in early 1980's monographs regarding advanced amphibious assault methods in the year 2000. Some units of the Russian Coastal Troops today even vaguely resemble the anticipated threat, but this monograph in particular shows the Marines were thinking about long range gunfire support in the 80's.

Over-The-Horizon Amphibious Operations: Will They Work?

www.globalsecurity.org

.

V-22 would outstrip the 5", even the 16", pretty quickly and mean more pressure on the attack helicopters, OV-10s, F-18s, and AV-8s to support the HLZs instead of interdicting incoming landing forces. It's only a paragraph because the monograph is more a brief overview of OTH assaults than a in-depth answer as to how to solve the problems, though.

 

[TomS]

The Marine NGFS expectation was built with the A-222 in mind? Very strong energy.

Whoops. No, sorry, my bad. It was designed around the D-30 -- 122mm not 130mm.

 

[GK Dundas]

I am somewhat amused by a comment by someone very early on in this thread. Who seemed less then impressed with the concept of heavy naval gun fire support. Something about not being used all that often any more .
No sees the need for almost anything up til the moment that you find yourself actually really needing that one thing. And usually the need is desperate.
I recall the RN had pretty much given up on Naval Gunfire Support starting in the late 50's right up until the Falklands . Any then suddenly...

 

[Scott Kenny]

I am somewhat amused by a comment by someone very early on in this thread. Who seemed less then impressed with the concept of heavy naval gun fire support. Something about not being used all that often any more .
No sees the need for almost anything up til the moment that you find yourself actually really needing that one thing. And usually the need is desperate.
I recall the RN had pretty much given up on Naval Gunfire Support starting in the late 50's right up until the Falklands . Any then suddenly...

In WW2, when people had 14"-16" guns available for shore bombardment, bunkers and their occupants would survive near-misses of battleship guns. Impacts so close the crater exposed much of the walls of the bunkers!

So it requires a direct hit from a 1500+lb shell to silence a well built reinforced concrete bunker, as on the Atlantic Wall or the islands in the Pacific.

But I see the call for artillery counter-battery fire onto wherever is shelling the helicopter LZs some 25nmi/40km inland, which does not require a huge shell but does require huge range from ships 25nmi offshore.