By Jay Bell

Sometimes what appears to be a good idea is not as good as it seems. That appears to be the case in the 40mm training ammunition world. The U.S. Army’s 40mm Day/Night/Thermal (DNT) effort has stalled and then restarted on the high velocity (M918E1) and on low velocity (M781E1) but has not successfully completed the First Article Acceptance Test (FAAT or FAT). These rounds were supposed to be a major leap in technology. They achieved several key requirements of the U.S. government. The Army got rid of a troublesome fuze in high velocity and added night training capability in low velocity in order to train like soldiers fight, at night. The magic material that made all this happen is called “pyrophoric iron.” Pyrophoric iron spontaneously combusts when exposed to air. It turns out that the pyrophoric iron may not be all it was cracked up to be. It has some serious downsides: It causes range fires, and allegedly, at least one round has gone off prematurely, flashing at 3,000 degrees with the gunner inches away.

Going Back

Now, the U.S. Army appears to be going back to decades-old technology to address the training requirements for the 40mm MK19 machine gun and M320/M203 weapons. The training ammunition for these platforms goes back to the later 1960s. The Army recently made an award to go back to the M918:M385 2:1 Mixed Belt configuration in December 2019. There was also a “Sources Sought” notice that came out in November 2019 to re-ramp for the projectiles, which were shelved a few years ago. The main producer had an auction in July 2019, since the DNT rounds appeared to be the path forward.

The Sources Sought announcement officially kicks off the procurement process for a 5-year “Indefinite Delivery Indefinite Quantity” contract to buy these 1960s technology, high-velocity projectiles. The high-velocity and low-velocity images are the old school rounds—a cutaway of the M918 Flash Band smoke and the M781. These images are courtesy of the U.S. government, and the comments are from one of the early Industry meetings highlighting the deficiencies circa 2014. Images of the M918E1 and M781E1 show only the outside of the new rounds. The insides are not available for public consumption. I attempted to get pictures from the Army, however, due to all the issues with the 40mm E1s, they were not letting any more pictures out. However, all of the market intelligence seems to point back to the 2004 Ted Haeselich patent, with chemical glow stick material in the middle of the round contained in a glass ampule (numbered 21/22). This ampule breaks and mixes upon setback to give a “lava” spurt downrange at night upon impact. The #13 item would be the standard orange powder or “signal dye.” This is to signal the impact area of the round.

Original U.S. government program timeline for the DNT program (see 2013).

A Little History

Since the 1990s, the 40mm high-velocity training ammunition option has been less than desired by the U.S. military. The 40mm M918 “flash, bang and smoke” round had multiple issues:

1) It had an expensive fuze that did not always function as desired and especially had problems in soft range conditions—sand, mud, wet, etc.

2) The fuzes did not have a self-destruct feature.

3) Projectiles that did not function are “unexploded ordnance” UXO and could cause injury if kicked or picked up.

4) The M918 was known to cause range fires that would shut down the training activities in some environments.

5) The M918 had a higher hazard storage and transportation class for the round.

The USMC became so fed up with the M918 situation that in the 1990s it stopped buying the Army’s M918 and started buying the MK281 from a small German company called NICO. The MOD 0 version had an orange signal dye like the Army’s low-velocity M781. Ted Haeselich worked at NICO in the 1990s and into the early 2000s. After an extensive adventure to fully type-classify the round, costing hundreds of thousands of dollars, the USMC made large purchases of the MK281. Later when NICO was purchased by German Military giant Rheinmetall, Rheinmetall started a U.S. manufacturing facility, and the orders skyrocketed. The original contracts to Germany were around $30M, and once they had the U.S. final assembly included, the contracts shot up to the $300M range. The story is a legend in the defense community.

Ted Haeselich’s patent with chemical glow stick material in the middle of the round contained in a glass ampule (numbered 21/22).

The MK281

The MK281 was perfectly simple. Basically, it is a high-velocity M781. It had a proprietary propulsion design that threads the projectile to the cartridge. The round must shear metal to fire, which is much more consistent than crimps and adhesives. The results are greater accuracy downrange. Later versions of the round added chemical luminescence aka glow sticks, to give a nighttime impact signature. It did not have a fuze, so there was ZERO chance of a dud. An additional plus is that the chemical luminescence materials are totally safe, ala Halloween glow sticks for kids. It can be eaten by kids on Halloween, and they can still eat all the candy they can handle. To meet the requirement of the DNT, the chemical properties were adjusted to add more heat to the process to be picked up with thermal imaging. The chemicals can be tweaked for colors, brightness, duration of glow and heat output.

The German cartridge design is favored by a lot of military forces around the world. Due to some old conflict over patents, the desire for 100% American-made products and a few other reasons, the MK281 has never seen full acceptance in the U.S. It does have one drawback, the chemical luminescence glows a rather long time. When you are training at night and shoot a large number of rounds, say 50 to 100, the target area will end up glowing so much that it is hard to tell when the last round hit. This phenomenon was coined as washout.

The Army Plan

The U.S. Army’s Project Manager Maneuver Ammunition Systems (PM MAS) started the planning for this next wave of development a long time ago. The 40mm DNT Industry Days date back to the early 2010s. The U.S. Army’s competition to solve its need for an improved M918 would be the M918E1 and in low-velocity M781E1. The M918/M781E1s had several key requirements:

1) No or minimal range fires (M918 only);

2) No fuze to fail and reduce costs (M918 only); and

3) Day, Night and Thermal visibility and/or signal (both rounds–new for M781).

PM MAS would have companies compete for the prize of making the rounds. The winning design would get the initial multi-year development contract and be in the leading position to make the rounds for the next 50 years. The M430 effects are the visual effects from an M430A1 HEDP round at 500m. The Army wanted a similar nighttime effect as seen in night vision.

On to the Competition

Nine companies submitted bid samples for evaluation in both 40mm high-velocity and low-velocity versions. These companies spent millions of combined dollars to get their designs mature enough to withstand the rigors of DOD testing. This field included American Ordnance (AO), Amtec, Chemring Ordnance, Cyalume Technologies, General Dynamics (GD), Rheinmetall, ST Kinetics (Singapore) and Universal Defense. Some did not even make it to the testing phase; some failed out early in testing.

These nine were down-selected to two competitors for high velocity—Amtec and AO Ordnance—and two for low velocity—Amtec and GD. Would the 40mm powerhouse Amtec, continue to dominate the 40mm world? Or would the large businesses with their success in ordnance in AO and general small/medium caliber ammunition expertise allow GD a win? Ultimately, it was AO as the high-velocity winner and GD as the low-velocity winner. The MK281 was in the mix along with several other varieties; however, it did not make the cut.

The competition had several deciding elements. The most important was pyrophoric or chemical luminescence. The best attributes of pyrophoric material were: a high heat output for thermal, bright visual light/explosion for the naked eye and lower hazard for storage and shipping. The best attributes of chemical luminescence were that it was totally inert and had zero risks of range fires. The negatives for pyrophoric was the “potential” for range fires. The downside of the chemical material was that it is difficult to see at 1,200m with the naked eye and the washout effect, as described above. The winning solution ended up being a pyrophoric solution for both rounds, which appears to be a key reason the programs have had so much difficulty.

Magic Material

Pyrophoric materials are processed iron particles that are contained in a glass ampule without air. When the ampule breaks and is exposed to air, it oxidizes quickly—actually, very quickly, which results in a lot of heat and a lot of light. It is technically a flash of light; some people might mistake it for a small explosion. The waste material is iron powder. It can be thrown away without concern about hazardous waste. It’s pretty awesome. The more interesting attribute is that if you break the top of an ampule off, the material will just simmer. You would just notice a color change and a slow process happening. If you turn the ampule over, you get a sparkler light show all the way down to the ground. If you smash it against the ground at 700m per second, you are back to the explosion-like effect.

The downside of pyrophoric material and what caused the program to be placed under a temporary Stop Work order is that the rounds were causing a lot of range fires—there was a safety incidence where the round in the chamber was broken and flashed in the weapon (potentially injuring the gunner)—and other performance issues. The M918E1 has a plastic ogive, and underneath it are some pretty powerful materials. The MK281 also has a plastic ogive; however, if this round breaks in the cycling of the MK19 machine gun, the glow stick material is not going to harm anyone.

Low-Velocity Status

The M781E1 delay issues are a little less well known. GD has not made it through first article testing, where AO is in production and has been awarded option quantities already. Is it the same pyrophoric range fire issues as M918E1, or is it something else? The drop test for pyrophoric could be to blame. The standard M781 could never pass a NATO standard 1M drop test. By the look of the design, I imagine that it would still be a problem. The pyrophoric material would make things interesting if it broke upon impact.

I have always been critical of the U.S. government’s typically painstakingly slow methods and processes. They test, test again and then test some more. Then repeat all those tests in multiple temperature phases. Once you are sure you have it nailed, they have someone else try to repeat the results exactly. It can be quite maddening at times, and you wonder how anything gets done. The 40mm DNT program seemed to be moving at light speed. It was extremely impressive. This current situation has given me a greater appreciation for taking it slow. The U.S. government goes slow when one item has been changed. In this case a little more so.

Pyrophoric materials have been successfully used in other military areas like aircraft countermeasure flares. However, it is still a newer process. The processes and applicant for 40mm had to be developed and built for these programs. Sometimes plans don’t work out at well as one would have hoped. This may be the case with pyrophoric—that it is just a little ahead of its time. There are a lot of people in the industry that think the M918E1 and M781E1 are doomed to failure. They believe the range fires might result in the M918E1 and M781E1 to be shelved, and we will go back to the 1960s designs, at least for a little while, and then either back to chemical luminescence or a newer material.

M918E1 the high-velocity round reducing the UXO hazard for the U.S. government.

The government’s original timeline from a 2013 Industry Day shows the program transitioning to full-rate production over / around 5 years. In reality, it took about 6 years. If they have to go back and re-invent the wheel, it will take another 5 years. These things just take time. This is one case where too new and not enough testing set things back, maybe a decade. Only time will tell.

The US Army’s programmes for developing two different 25mm grenade launchers – the shoulder-fired XM25 from Alliant Techsystems and the crew-served XM307 ACSW (Advanced Crew-Served Weapon) by General Dynamics – are probably the most ambitious small arms projects in existence.  They are meant to revolutionise the effectiveness of small-arms fire by detonating HE/fragmentation grenades directly over the target, thereby greatly increasing the number of casualties, not just of standing men but also those hiding behind cover.  Such rounds are known as HEAB (High Explosive Air Burst) or ABM (Air Bursting Munition).

To achieve this requires some sophisticated technology.  The XM307 is fitted with a day/night sight with a laser rangefinder, a ballistic computer and a fuze-setter.  The gunner first lases the target to establish the range (this can be overridden if the target is at a slightly different distance than the aiming point); the system then takes atmospheric conditions and weapon tilt angle into account before indicating the aiming mark in the sights.  The gunner can set the fuze mode for airburst, PDSQ (point detonating super-quick), PD delayed-action or deactivate; it also contains a self-destruct element.  The projectile fuze measures the distance by counting the number of rotations: its spin rate is 21,000-28,000 rpm. The XM25 uses the same technology, with a shorter, lower-velocity cartridge limiting the range to around 700m rather than 2,000m.

The XM307 was originally intended to replace most of the .50 M2HB and 40mm Mk 19 AGLs, while the nearest comparators to the XM25 are the much bulkier six-shot revolvers chambered for the low-velocity 40mm grenade round, such as the  Milkor MGL, adopted by the USMC as the M32.  Adoption of the XM25 might therefore be expected to lead to a reduction in the use of the 40mm LV (low velocity) weapons, if not their eventual disappearance.

The manufacturers of 40mm GLs and ammunition are not taking this lying down, however, and have come up with a range of new developments to keep their products attractive.

Ammunition for Shoulder-Fired Grenade Launchers
The 40x46SR low velocity (LV) grenade round has now been around for almost half a century, originally chambered in stand-alone single-shot guns like the M79, but subsequently in underbarrel grenade launchers (UGL) such as the M203, and more recently the six-barrel revolvers mentioned above.  The muzzle velocity is only 250 fps, limiting the maximum range to about 400m.

The original round fired was the M406 HE/fragmentation type, and High Explosive Dual Purpose (HEDP) rounds have also been available for some time, enabling these launchers to be used to tackle light armour.  Some recent developments have considerably extended the versatility of this round.  From Arcus of Bulgaria comes the AR476 “Anti-Diver” grenade which has a time fuze which is set on impact with the water, detonating the HE at a stated depth of between 5 and 12 metres and with a claimed lethal radius of 12m.  They have also introduced the AR466 “Bouncing” ABHE grenade which on impact is kicked back up into the air by a small nose charge before detonating, to increase the lethal radius – not a new idea, but a very much cheaper way of providing some of the effectiveness of the sophisticated HEAB systems.  A similar RLV-FJ “Jump” round is offered by Arsenal, also of Bulgaria – a country which appears to be innovating with enthusiasm in this field.

More effective conventional ammunition has also been developed, with the latest trend being Medium Velocity (MV) rounds, with the muzzle velocity increased to between 350 and 410 fps, thereby doubling the effective range.  Recoil is claimed to be similar to that of a 12 gauge shotgun, and well below that of a rifle grenade, and they are designed to be used in many existing LV systems.  At a range of 150m the mid-range trajectory will be halved to about 3m and flight time is reduced.  The first in the field was Martin Electronics’ “Mercury”, which is significantly longer than standard 40mm HE rounds to make room for a larger HE charge, doubling the destructive power as well as the range of the conventional M433 HE grenade.  Nammo Raufoss, Heckler & Koch and now Denel of South Africa are also developing MV ammunition, while Arcus have developed “extended range” versions of their HE and ABHE products, capable of about 600m.

IMI and STK are even developing High Explosive Air Burst LV rounds to deliver the same effects as the XM25, although these do of course need to be used in conjunction with special sights with a laser rangefinder and fire control computer, and also a launcher modified to include an electronic fuze setter.  IMI have developed the compact and lightweight Orion sight which offers these facilities and can be fitted to any rifle in conjunction with a modified UGL.

Martin Electronics 40mm LV “DRACO” thermobaric grenade.

Martin Electronics have also introduced a thermobaric round, the DRACO; a type of explosive which is proving particularly popular in some larger weapons in use in the Middle East because of the effectiveness of its high blast overpressure in enclosed spaces such as buildings and caves.  The round is very expensive, however, so attention is now being focused on the much cheaper Hellhound.

The peacekeeping roles which armies frequently have to adopt have generated growing interest in Less-Lethal ammunition for riot control and similar policing activities.  Many manufacturers now offer a very varied range of irritant chemical, impact, combined and paint marker ammunition too extensive to describe here.  Although such munitions have traditionally been used in specialised 37/38mm riot guns, they are increasingly available for the 40mm LV grenade launchers – and, in a few instances, for the 40mm HV AGL as well.

Other types of rounds which are not directly lethal include various smoke and flare types.  There are also some novel developments, most notably the observation rounds containing parachute-borne video cameras that send pictures directly back to the operator, providing an instant view of what lies over the hill or around the corner.  Both STK (with the SPARCS) and Martin Electronics (with the HUNTIR) have developed such rounds for 40mm LV grenade launchers, while the Rafael Firefly, still in development, is equipped with folding “wings” rather than a parachute.

Many of the new rounds are longer than standard, at up to 5.5 inches.  In contrast, ammunition for the semiautomatic XM25 is limited in size (the maximum length is only about 3.5 inches), and cannot hope to emulate the variety of types now available for the 40mm LV GLs, which will be with us for the foreseeable future.

40mm AGLs
The success of the original 40mm LV grenade rounds rapidly led to the development of fast-firing weapons chambered for them, but almost as quickly the need for greater range was realised, so the 40x53SR high velocity (HV) cartridge was developed.  This had the muzzle velocity increased to around 800 fps which, in conjunction with a heavier grenade (about 240g compared with 180g), increased the effective range out to 2,000m.  The first automatic grenade launchers (AGLs – also known as grenade machine guns or GMGs) chambered for this round were externally powered and designed for installation in helicopters: the M75 and M129 both seeing service in Vietnam.  Far more important, however, was a self-powered design, the Mk 19.  This was developed in the late 1960s as a USN project but was subsequently adopted by other services, as well as achieving substantial export sales.

Since then, and particularly since the 1990s, a number of rival AGLs have emerged from several different countries: the Spanish Santa Barbara (now General Dynamics Santa Barbara Sistemas) LAG 40 SB, the Singapore Technologies Kinetics (STK) 40AGL and Light Weight AGL, the Heckler & Koch HK40 GMG (recently bought by the British Army), South Africa’s Denel Y3 AGL, and other weapons from Romania, Poland, Turkey and Pakistan.  Of most significance to the USA is the CG40, a joint project between three companies, commencing in 1995: Nammo (ammunition), General Dynamics Canada (Fire Control) and Saco Defense (now a part of GD) who developed the gun and dealt with system integration.  Some 400 are in service with US special forces, ordered between 2001-5, under the designation Mk 47 Striker.

The HV ammunition used in these guns has not shown the variety found in the LV rounds, partly because of the narrower range of uses of the AGLs and partly because the need to function in an automatic mechanism restricts the characteristics – and particularly the overall length – of the cartridge.  However, a great deal of attention is now being paid to the development of the same kind of airburst technology as that being tested in the XM307.

Nammo 40mm HV PPHE rounds.

The way is being led by Nammo Raufoss, who have developed HEAB ammunition as a part of the CG40 project, under the designation PPHE (Programmable Pre-fragmented HE).  The gun was designed for this from the start, the necessary systems being integrated into the weapon.  These include an image-intensifying video sight linked to a laser rangefinder and incorporating a ballistic computer to indicate the exact aiming point, and an electronic fuze setter by the gun breech.  When used with the appropriate ammunition fitted with the Mk 438 programmable time fuze, the system sets the appropriate time delay on the fuze while it is in the chamber (the gun fires from a closed bolt) so that the grenade bursts directly over the target.  The gun can also use conventional point-detonating 40x53SR ammunition, with which the advanced sights are still useful in providing a high level of accuracy.  The Mk 285 HEAB projectile produces fragments which are mainly distributed sideways and backwards to catch troops behind cover, rather than forwards as with a conventional grenade.  An initial order for 39,000 of this round has been placed for use in the Mk 47 Striker, with deliveries expected to be completed by early 2008.

Nammo are also working on a variation of this system for guns, such as the HK40 GMG, which fire from an open bolt.  The chosen system is radio frequency programming, the fuze being set about 4 to 5 metres after the grenade has left the muzzle.  Since all of the system requirements are contained within a single sight/fire-control/programming unit, this can be fitted to any gun able to mount the unit.

There is yet a third HEAB system, from STK of Singapore; the ABMS (Air Bursting Munition System), which can also be fitted to existing 40mm AGLs.  This was developed in conjunction with Oerlikon-Contraves Pyrotec AG of Switzerland, who adapted the technology developed for their 35mm AHEAD cannon ammunition.  As with AHEAD, the fuze-setting system is attached to the muzzle and sets the fuze as the grenade leaves the barrel.  Like the Nammo systems, special grenades are used with an all-round fragmentation pattern, so they throw fragments behind them as well as in front and to the sides; the Oerlikon/STK type contains 330+ tungsten balls, each weighing 0.25g and intended to penetrate at least some grades of body armour.  The effective range of the system is 40 to 1,600m.

Sectioned 25x59B HEAB for XM307 ACSW.

In the rush to airburst systems, the value of the conventional (and much cheaper) ammunition has not been forgotten.  Nammo have developed a ‘product improved’ M430 HEDP round at the request of the USMC, who have asked for a mechanical self-destruct fuze, a modified (NICO type) propulsion system, insensitive munition (IM) properties using a PBXN-11 main charge, additional incendiary after-armour effect, penetration improved from three to four inches of RHA, and a reduced safety zone to prevent the base of projectile from being blown back towards the gunner (the current limitations being 310m in peacetime, 75m in wartime).  Internal Nammo qualification of this round is expected in spring 2008.

While the 25mm XM307 offers certain advantages, notably gun and ammunition weight plus a much flatter trajectory and shorter flight time, the 40mm AGLs clearly have a lot of life in them yet.  Their ability to fire inexpensive standard ammunition as well as sophisticated HEAB rounds means that they are likely to remain popular long after the XM307 enters service.