US Navy Discloses 155mm Advanced Gun System’s Preliminary Fate

55mm Advanced Gun System AGS
Each DDG-1000 destroyer has two 155mm Advanced Gun System cannons on the forward section. These guns will be removed to make way for 12 Conventional Prompt Strike hypersonic missiles. (Photo: US Navy)
The U.S. Navy’s Naval Sea Systems Command (NAVSEA) has disclosed to Naval News the initial fate of the Zumwalt-class stealth destroyers’ Mark 51 155mm/62 (6.1”) Advanced Gun Systems (AGS) that will be removed for the installation of 12 Conventional Prompt Strike (CPS) hypersonic missile launch tubes.
Share
Zumwalt-class destroyers' 155mm AGS will be placed into storage

Naval News has been pursuing this question for some time: Will the 155mm Advanced Gun Systems (AGS) be saved and stored, destroyed in the removal process, or scrapped?

Designed as long-range offshore fire support for a potential U.S. Marines’ amphibious landing, the stealthy Mark 51 155mm/62 (6.1”) AGSs were supposed to be the largest caliber of offshore naval gunfire support aboard a U.S. Navy warship. However, their ammunition magazines and automated loading were not designed to fit, handle, and fire U.S. Army and NATO-standard 155mm howitzer shells due to differences in the shape and size of the projectile and firing charges, thus requiring special custom GPS Long-Range Land Attack Projectiles (LRLAP) costing around $800,000+ each due to the reduction of Zumwalt-class destroyers from 32 to 3.

This exorbitant cost of each shell rendered the AGSs useless for years even though the guns could, in theory, fire at 83 nautical miles (150 kilometers) at 10 rounds-per-minute with LRLAP.  A whopping 335 155mm rounds can be carried aboard each AGS, or 670 rounds for both 155mm AGSs. There is also an auxiliary storeroom separate from the automated ammunition handling system that can hold an additional 320 rounds and would require the manual transfer of the rounds to the guns’ magazines. Therefore, one Zumwalt-class destroyer has 990 rounds of 155mm AGS shells.

The AGS barrels are nestled in stealthy angular structures that hid the highly reflective metal barrel in a trench from enemy ship radars and sensors. Only when ready to fire would the gun barrels elevate outwards, rotate, and fire.

155mm AGS
Artist’s impression of the forward 155mm AGS firing and the rear one housed in the turret. (Image: DDG(X) National Team)

For years, NAVSEA debated on what to do with the non-fuctional 155mm AGSs. The public posted online comments such as design and acquire cheaper shells, remove them for more Mark 41 vertical launch system (VLS) cells, or even replace them with high-tech railguns. NAVSEA has finally answered on May 19, 2023 as to the 155mm AGSs’ initial fate.

“In response to your question on the 155mm Advanced Gun System (AGS), there is no update to provide at this time.  They will be placed into storage and the disposition remains to be determined.”


NAVSEA Spokesperson, May 2023

12 Conventional Prompt Strike hypersonic missiles are intended to replace the two Mark 51 155mm AGSs.

Naval News and Author’s Comments

The disclosure to store the 155mm AGSs is revealing in that NAVSEA determined that the AGSs are worth saving to some degree and not cut up, destroyed outright, and scrapped in the dismantling process.

A total of six Mark 51 155mm/62 (6.1”) AGSs exist, two guns on each DDG-1000 destroyer. As to what state and degree of dismantling the 155mm AGSs will be when placed into storage remains unclear. Also unknown is if the 155mm AGSs can be used again for another class of ship, and to date, no future U.S. Navy ship design exists that intends to utilize the 155mm AGSs. The next-generation destroyer, the DDG(X), purportedly shows a 5-inch gun on the bow, even though that is a preliminary design graphic. One conceptual naval vessel does include the 155mm gun and that is the UXV Drone Carrier Warship which Naval News wrote an Op-Ed in April 2021.

Even if the UXV Drone Carrier Warship became a reality and was built in the future, it would make more logical sense if NAVSEA went ahead and used U.S. Army howitzer guns such as the 155mm Extended Range Cannon Artillery (M1299 ERCA) that fires the entire U.S. Army and NATO-standard 155mm shell inventory than resurrect the ammunition-less Advanced Gun Systems that requires custom shells to be made. While the M1299 ERCA cannot fire out to 150 kilometers like the AGSs, it can reach out to at least 70 kilometers with a rocket-assisted round and with the planned ERCA autoloader, can fire 10 rounds-per-minute. Nonetheless, this is all hypothetical thinking as there are no publicly disclosed current and future plans within NAVSEA to design and build a future hybrid Drone Carrier Warship.

A conceptual artist’s rendering of the UXV Drone Carrier Warship showing its AEGIS radars and VLS cells in addition to two split runways. The bow has a 155mm cannon for naval gunfire support of amphibious landing forces. This remains the only conceptual warship design that incorporates a 155mm cannon. However, there is no indication that the U.S. Navy is interested in designing and building such a hybrid Drone Carrier Warship with split runways, or using the 155mm AGS ever again. (Image: Kollected Ltd)

Once removed, if the DDG-1000s’ six 155mm AGSs will ever be resurrected in the future seems murky as the AGSs never did have much of a purpose without shells to fire. If they ever do see a resurrection, they would need a total revamp of their automated ammunition handling facilities to accommodate and fire much cheaper and plentiful 155mm U.S. Army and NATO shells and do away with the U.S. Navy’s super-expensive LRLAP shells.

That can be a possibility if the U.S. Navy builds new automated ammunition handling magazines underneath these AGSs, preferably not on a warship. Perhaps all six removed AGSs can find new life on the perimeter of Guam, on an island, at a strategic choke point, or at an important port to act as defensive coastal artillery against an amphibious invasion. While World War Two-like fixed site coastal gun batteries are outdated in belief in today’s age of advanced Long-Range Precision Fires (LRPF) missiles, when combined with defensive land-based surface-to-air missiles (SAMs), AEGIS Ashore, AEGIS warships, and counter-rocket, artillery, and mortar missiles (C-RAM) to shoot down incoming enemy missiles, these land-based 155mm AGSs might have a fighting chance against enemy LRPF missiles to survive and fire back and act as an effective gunfire support as they were originally intended.

Two soldiers stand beside the U.S. Army’s Long-Range Hypersonic Weapon’s (LRHW) two box launchers on a trailer in a good visual example of the LRHW’s length and scale. The U.S. Navy uses the same LRHW missile, renamed the Conventional Prompt Strike (CPS) missile. 12 CPSs will go into each DDG-1000, or 36 CPS hypersonic missiles for all three stealthy DDG-1000 destroyers.  (Photo: US Army)

Advertisement

Advertisement