Northrop Grumman starts production of M1156 PGK E5 guidance kits to improve artillery fire under GPS jamming.

Northrop Grumman initiated production of the M1156E5 Precision Guidance Kit at its facility in Plymouth, Minnesota, following a U.S. Army contract configuration update. The next-generation anti-jam assembly integrates into existing 155 mm artillery inventory. This design maintains standard form factors while preserving target accuracy in GPS-degraded combat environments.

The M1156E5 kit retains a nose-mounted 1.4 kg architecture that replaces conventional fuzes on standard high-explosive projectiles without requiring complete guided rounds. Recent testing under electronic interference demonstrated performance meeting established threshold and objective accuracy metrics ahead of scheduled 2028 deliveries.

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The M1156E5 Precision Guidance Kit (PGK E5) is a guidance and fuzing kit that converts compatible 155 mm artillery projectiles into GPS-guided rounds able to maintain less than 30 m CEP accuracy in GPS-degraded environments. (Picture source: Northrop Grumman)

On September 9, 2026, Northrop Grumman announced that the production of the M1156E5 Precision Guidance Kit (PGK E5) had started in Plymouth, Minnesota, with first deliveries of the U.S. Army's next anti-jam 155 mm guidance kit scheduled for early 2028. The E5, also known as the NA38 configuration, retains the basic PGK architecture: a 1.4 kg nose-mounted assembly replaces the conventional 155 mm fuze with an integrated GPS receiver, flight control system, and fuze, allowing the U.S. Army not to purchase a complete guided artillery round. Its accuracy requirements remain below 50 m CEP at threshold and below 30 m at objective, but the principal E5 improvement is its enhanced GPS anti-jam capability for a peer-threat environment. Reliability requirements are above 92% at threshold and above 97% at objective, respectively. GPS-degraded testing exceeded both accuracy requirements, establishing performance below 30 m CEP under the tested interference, jammer power, J/S ratio, emitter distance, number of jammers, and achieved CEP remain undisclosed. Northrop Grumman is the prime contractor, and L3Harris supplies the GPS component, as more than 145,000 PGKs have already been delivered.

The baseline M1156 Precision Guidance Kit (PGK) weighs 1.4 kg and measures 220.2 mm overall, including 95.25 mm outside the projectile and 124.7 mm inserted into the fuze well, making it 0.45 kg heavier than a conventional fuze. Inside that volume are the GPS receiver, guidance electronics, fuzing components, flight control hardware, and an alternator that generates electricity after launch, eliminating a battery and supporting a 20-year shelf life. Four aerodynamic controls correct the ballistic trajectory during flight, as the electronics compare GPS-derived position with programmed target coordinates. The same assembly provides point-detonating and proximity functions and fits a NATO-standard deep-intrusion fuze well. The E5 retains the existing PGK mass and form factor, so its principal physical interfaces with the projectile and howitzer remain unchanged.

The accuracy difference can be quantified more usefully against the M549A1 HERA, which has a cited 267 m CEP at maximum range, meaning that 50% of rounds would statistically fall inside a 267 m-radius circle under the relevant firing conditions. A 50 m PGK threshold reduces that radius by 81.3%, while a 30 m objective reduces it by 88.8%. Because area changes with the square of radius, the corresponding CEP circle contracts from 223,969 m² at 267 m to 7,854 m² at 50 m and 2,827 m² at 30 m, respectively 28.5 and 79.2 times smaller. Actual test groups have sometimes been tighter: a June 2015 lot-acceptance firing produced a median accuracy below 10 m, while September 2014 trials with German DM111 projectiles fired from a PzH 2000 at 27 km placed 90% of the rounds within 5 m of the target. In April 2015, 41 of 42 rounds fired from an M109A6 Paladin functioned successfully, equivalent to 97.6%, providing an early production reliability result close to the current greater-than-97% objective. These results did not change the formal requirement, and the PGK remains less accurate by requirement than the roughly 6 m figure associated with the purpose-designed M982 Excalibur.

In fact, the E5 addresses GPS interference due to electronic warfare, rather than increasing a 155 mm round's nominal accuracy. Standard PGK receives GPS position updates during flight and uses them to calculate trajectory corrections, so degraded navigation signals directly reduce the quality of the information available to the guidance loop. The PGK E5 therefore retains the less-than-50 m threshold and less-than-30 m objective while attempting to prevent the existing accuracy requirement from collapsing as GPS reception deteriorates. The September tests establish sub-30 m performance under the specific interference applied, but they do not establish the maximum jamming environment E5 can tolerate because effective radiated power, frequency coverage, J/S ratio, and jammer geometry are unavailable. Moreover, the E5 should not be treated as a GPS-independent artillery round: no inertial, imaging, laser, or terminal-seeker backup has been specified to maintain 30 m accuracy after complete GPS denial.

The kit is integrated with the M109A6 and M109A7 Paladin self-propelled howitzers, as well as the M777A2 Lightweight Towed Howitzer, and is compatible with the XM1113, M1128, M795, and M549A1 155 mm HE projectiles. The M1128, for example, carries 9.07 kg of IMX-104, reaches 30 km from a 39-caliber gun, and accepts the M1156E5, although installation of a PGK reduces its range by 10%, implying a PGK-equipped maximum of roughly 27 km under that stated condition. The PGK also incorporates a safety function separate from CEP: five seconds after launch, the established system evaluates predicted impact, with a 150 m no-fire function available to inhibit detonation when the calculated miss is excessive. U.S. Army configuration data further identify NA36 as introducing a selectable 150 m no-fire radius, NA29 as incorporating reliability improvements and M1128 compatibility, NA37 as adding hardware and software changes for M-code GPS, XM1113 compatibility and M1128 optimization, and NA38 as the E5 anti-jam configuration. E5 is therefore one step in an incremental configuration sequence rather than a complete redesign of the M1156.

The manufacturing baseline extends back almost two decades. Alliant Techsystems received the PGK development contract in May 2007, Fort Bliss soldiers fired 24 XM1156-equipped projectiles in October 2012, and the first NA28 configuration reached Afghanistan in April 2013. Production reached 4,779 kits by mid-2016, exceeded 25,000 by April 2018, and has now passed 145,000 deliveries, while the family has recorded 98% point reliability since 2013. Northrop Grumman is producing the E5 using the existing PGK production line, suppliers, and resources rather than establishing a separate manufacturing system. A June 2025 Army modification provided $26.95 million for M1156E5 development, qualification, and production through May 21, 2028, while the FY2026 ammunition budget identifies higher unit and production-engineering costs as procurement shifts from NA37 M1156A1 to NA38 M1156E5, which is intended to become M1156A2 after Type Classification.

PGK's earlier cost objective was below $10,000 per kit, while another production figure placed M1156 at $13,541; no equivalent E5 unit price has been released. Foreign procurement provides scale but not directly comparable unit prices: Australia's 2013 request covered 4,002 kits plus support for $54 million, or $13,493 per kit by simple division; the Netherlands' 2018 package covered 3,500 for $70 million, or $20,000; Finland acquired roughly 5,500 M1156A1 kits for $70 million in 2024, or $12,727. The broader modernization path addresses separate variables: M1156E2/A1 planning targeted 10 m accuracy with XM1128 at 30 km and XM1113 at 40 km from 39-caliber guns, while Long Range PGK targeted 70 km from a 58-caliber gun, 75% farther than the 40 km case. E5 does neither. It retains the 30-50 m accuracy requirement and existing ammunition interfaces while addressing GPS jamming, making navigation resilience, rather than range or nominal CEP, the principal performance change entering production for FY2028 fielding.

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Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, South Korea, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.