Here’s what you’ll learn when you read this story:

• The Navy is trying to revive a controversial supergun program alongside a new Trump-class battleship.
• Superguns are huge pieces of artillery that fire projectiles across unmatched distances and are generally placed in a fixed position.
• None of the Pentagon’s past supergun endeavors have panned out; it’s unlikely that this time will yield different results.

Generals and politicians alike have long been fascinated by big guns, which besides their Freudian aesthetics offered specialized utility, cracking open fortifications or armored warships over very great distances, even when too heavy for practical general-purpose use. Though the most titanic of these weapons have fallen out of use and been overtaken by missiles, to this day the Army and Navy continue to look for ways to bring them back. This despite multiple failed attempts. This despite the physics.

During World War II, sailors and soldiers witnessed duels between monstrous super heavy guns the likes of which have not been seen since. In the 1944 Battle of Surigao Strait, American battleships pivoted their radar-directed triple-gun turrets, huge plumes of combusting propellant spouting from their barrels like dragon fire as they lobbed 16-inch shells weighing 1.4 tons each at heavily armored Japanese battleships up to 11 miles away.

Earlier that year on the other side of the globe, GIs mired in the muck of the Anzio beachhead in Italy scrambled for cover as a sound like a careening freight train announced a terrifying salvo from two massive German railway guns nicknamed “Anzio Annie.” These belted huge 280-millimeter rounds across distances of up to 40 miles to sink ships in harbor, blast landed warplanes, and detonate ammo depots. The U.S. Army fought back with its own huge Black Dragon M1 240-millimeter guns, attempting to collapse the railway tunnels Anzio Annie used for cover.

But World War II was the high watermark for such beastly weapons, which gradually lost relevance as new missiles and improved rocket artillery offered more practical ways to assail tough, distant targets from farther away with greater precision and mobility. By the 1990s, the U.S. Army finally retired its last M110 8-inch super-heavy self-propelled howitzers and the Navy its last battleship, the USS Pennsylvania with its 16-inch/50-caliber Mark 7 rifled guns.

Yet it wasn’t long before the services tried to bring bigger guns back—always hoping new precision warfare technologies could restore big guns as cheaper alternatives to expensive missiles. Most recently, the Trump administration’s controversial new plan to build neo-battleships appears to have revived the Navy’s railgun program that was canceled several years earlier. Meanwhile, the Army’s SPH-M program is expected to soon announce yet another candidate for a new self-propelled howitzer with a much longer, far-shooting gun barrel than its current M109 Paladin vehicles, following the failure of two prior attempts.

However, these projects must overcome the engineering challenges that caused so many past attempts to fail: big guns transmit huge stress to the gun’s barrel, often end up requiring expensive special ammunition, and contribute bulk and cost to platforms that risk obviating their theoretical efficiencies. The history speaks for itself.

M1299 Extended Range Cannon Artillery

During the 1990s and 2000s, the Pentagon was more worried about the difficulty of moving heavy artillery across the globe and less about how far it could shoot. That led to the 2002 cancellation of the Army’s beefy 40-ton next-generation tracked howitzer called the XM2001 Crusader.

But by the 2010s, the U.S. Army grew concerned that its towed M114 and self-propelled M109 howitzers had fallen behind the range of Russia’s longer-barreled 2S19 and China’s PZL-05 howitzer—a concern which finally prompted the service to seek a longer-barreled howitzer called the M1299 Extended Range Cannon Artillery (ERCA).

Two traditional ways to increase artillery range include lengthening the gun barrel and increasing diameter. Longer barrels allow greater pressure to build up, which squeezes shells out at greater speeds, while a larger diameter accommodates larger propellant charges. However, the barrels on bigger guns, themselves, must increase in robustness and weight to withstand increased pressure; likewise, their carriages must have sufficient bulk to absorb the greater recoil. That piles on weight, cost, and complexity.

To avoid those upsizing problems, post-World War II militaries have instead mostly sought ways to increase range using standard-caliber howitzers ranging between 105- and 155-millimeter diameter, leveraging advancements in propellant chemistry, gun barrel metallurgy, and exotic ammunition including base-bleed rounds that expel gas to reduce drag and improve stability, and even rocket- or ramjet-assisted rounds. The M1299 retained the chassis and 155-millimeter shell diameter of the service’s mainstay M109, but achieved greater range with a 50 percent longer XM907 gun and advanced new shells. In successive tests, it sstruck targets from 38, 40, and 43 miles away.

But while the M1299 could execute impressive long-range shots even on a van-sized target, it had a big fundamental flaw: each shot stressed the XM907’s barrel so greatly that it required very frequent replacement compared to a standard M109 howitzer, which is rated to perform 1,500 to 2,500 shots using the maximum quantity of propellant before a barrel change is required. In intense combat conditions, frequent barrel replacement would be impractical and undermine the whole point of having artillery that can generate sustainable long-distance attacks.

Barrel wear afflicts all artillery, especially when executing longer-range shots using the maximum quantity of propellant charges. Worn barrels initially degrade in accuracy, but upon exceeding life expectancy, they’re at growing risk of an explosion petalling the barrel open like a cannon in a Looney Tunes cartoon.

Thus, despite procuring a battalion of M1299s, the Army canceled the system in 2023. A new program called SPH-M is seeking to produce a less ambitious alternative with a 52-caliber barrel.

Strategic Long Range Cannon

If 40-mile shots sound impressive, the Pentagon had even wilder ambitions for its concurrent Strategic Long Range Cannon (SLRC or earlier LRSC) aimed at striking targets over 1,000 miles away. In 2020, photos leaked revealing the proposed design involving a massive gun towed by a trailer.

In truth, SLRC was a big gun that spat out missiles. Being shot from a gun removed the need for launch boosters, giving a big boost in range, speed, and altitude before the missiles’ primary rocket/jet motors ignited. Theoretically, such gun-launched missiles could approach the range of Tomahawk cruise missiles but cost only one-third or one-quarter as much—perhaps $400,000 per shot.

The idea was for the SLRC to sustainably and cost-efficiently strike distant “anti-access” weapons like air defense and anti-ship batteries that might otherwise prevent the Navy and Air Force from operating freely.

But designing a 30-foot-long gun barrel proved extremely challenging, and actually using this weapon would have required solving many practical problems regarding how they would be deployed, protected, and supplied with targets abroad.

Ultimately, Congress canceled the program, judging the cost of development and deployment unfavorable compared to the cost of existing long-range missiles. Indeed, the Army now relies on missiles shared with the Navy—Tomahawks, SM-6s, and Dark Eagles—for long-range strikes instead.

Advanced Gun System

By the 1960s, anti-ship missiles with far greater range and accuracy began making the large and numerous gun batteries of older warships obsolete. Today, modern warships typically sport just one 3- to 5-inch gun and a few smaller self-defense autocannons.

But in the 1990s, the Navy began looking to deploy warships armed with multiple 155-millimeter guns that could shoot across super long distances. Why? Post-Cold War, the U.S. Navy faced no serious challengers, so the thinking was to build ships to cost-efficiently wage coastal (“littoral”) warfare against countries with weak navies like Iran and North Korea.

The Navy’s then-next-generation destroyers, the Zumwalt-class, were therefore designed to use two long-range 155-millimeter Advanced Gun Systems (AGSs) with 62-caliber length barrels as their primary weapon to cost-efficiently strike coastal targets from dozens of miles away.

British defense contractor BAE Systems built six AGSs, each massing 104 tons for the initial three Zumwalts. Enhanced with fully automatic firing and loading systems, they could blast up to 10 rounds per minute, drawing from a magazine of 300 shells each.

But despite sharing the Army’s standard howitzer caliber, AGS was incompatible with standard shells, instead relying on advanced rocket-assisted smart rounds called Long Range Land Attack Projectiles (LRLAP), which use GPS guidance to land shots within 165 feet of a designated target on average. The 225-pound rounds could theoretically achieve a maximum range of 95 to 115 miles, per various sources.

Shell manufacturer Lockheed Martin estimated in 2004 that LRLAP rounds might cost $35,000 per shot if mass-produced. But because LRLAP was a nonstandard round built to arm just three ships to start, the initial order of 150 rounds averaged more than ten times that, coming in at $450,000 per round in 2010—then doubled to $900,000 per shot by 2016, approaching cruise missile prices.

Hypothetically, bulk purchases down the road might have reduced costs, but the Navy had had enough and canceled the LRLAP program. By then, even if AGS ammo had been cheaper, it was clear Zumwalt’s gun-based littoral warfare concept was hopelessly outdated given the growing long-range threat posed by China’s navy and land-based anti-ship missiles.

The Navy studied converting AGSs to fire Army-standard rounds, including the M982 Excalibur smart shell, but found it would still require $250 million in modifications to implement. Ultimately, Zumwalt procurement was halted at three ships, and the AGSs were ripped from their decks—to be replaced with experimental launch capability for hypersonic missiles.

Railguns

Meanwhile, in 2005, the Navy began seriously pursuing a more futuristic weapon: the railgun (not to be confused with the train-mounted railway gun). These use two parallel rails that generate magnetic fields to accelerate a projectile between them to fantastically high speeds approaching Mach 8. That creates enough energy to traverse huge distances and destroy targets purely based on kinetic energy without requiring a warhead.

It had been successfully tested in U.S. laboratories since 1980, but now the U.S. Navy planned to evolve its electromagnetic railgun (EMRG) into a practical ship-board weapon firing 155-millimeter diameter aerodynamically optimized ammunition called Hypervelocity Projectiles exceeding five times the speed of sound.

Railguns have appeal compared to missiles because they don’t require propellant and attain such enormous kinetic energy they can massively damage targets through impact alone without explosive warheads. Ammunition incorporating little or no explosives and propellant is smaller, cheaper, and much safer to store on warships than missiles. Finally, the tremendous speed of railgun shots gives them potential to intercept speedy incoming missiles, or conversely, help avoid interception by enemy defenses if used offensively.

However, railguns require a huge amount of electrical energy, exceeding the capacity of most ground vehicles, leaving warships (already built to generate a lot of electricity) as the practical platform. But even on ships, railguns still compete with other energy-hungry systems such as radars, self-defense jammers, and eventually lasers. Therefore, integrating railguns likely requires new, larger warships built for greater electrical generation.

The solid shots from railguns would also require extremely precise targeting information (including predictive targeting for moving targets), as the limited blast radius leaves little room for error.

Yet again the nail in the coffin for Navy railgun tests proved to be a kind of “barrel wear”: the recoil stress on the electromagnetic rails from each shot proved so intense that they required replacement after just 30 shots—far short of the desired 1,000-shot life expectancy. After spending 15 years and a half-billion dollars, the U.S. Navy canceled its railgun program in 2021.

We haven’t heard the last of railguns, though, as China and Japan continue their own research and development programs. Since 2023, Japan has test-fired the first sea-based railgun from the ship Asuka, achieving Mach 6.5 speeds and longer rail lives (over 120 shots without failure). But Japan’s program differs from America’s because it involves a smaller 40-millimeter round aimed exclusively at air defense; the rails also integrate a new alloy to reduce barrel erosion. The U.S. Navy itself resumed railgun tests this March, as the big new battleship introduced by President Trump is a natural fit for such weaponry—if it can be made practical, that is.

Ultimately, railguns remain a highly intriguing weapon thanks to the potential low cost of ammunition, difficulty of interception, and dual application for defensive and offensive missions. But big challenges surrounding sustainable practical use need to be solved.

The underlying challenge of modern supergun programs is that they seek to offer cheaper long-range strike alternatives to missiles and drones. But finding a solution that’s logistically practical and doesn’t require expensive, exotic ammunition is proving difficult for the very reasons guns began vanishing from use in the first place.