Longer, Faster, Better Boom for Your Buck
by Adam Baddeley, SOTECH Correspondent
New medium velocity (MV) 40 mm grenades offer a significant boost in range and terminal effects over those currently in service with the ubiquitous M203 and XM320/ AG36 underbarrel grenade launchers, providing a means of small tactical units to extend their reach from just 400 meters to 800 meters using the same launcher. Torsten Bohm, senior vice president, Product Division Infantry, Rheinmetall Waffe Munition GmbH, responsible for developing MV rounds for use with the SOF Combat Assault Rifle (SCAR) program, outlined the environment in which MV rounds will be introduced. “You currently have two grenade systems: low velocity (LV), which was designed during the Korean War to close the gap between the hand thrown grenade and the light mortar and the crew served; and high velocity grenade machine guns, which were first fielded during the Vietnam War, mainly for riverine missions.”
Medium velocity promises several benefits over current low velocity solutions. MV allows for shorter time of flight to reach the enemy more quickly and flatter trajectory to make the rounds more accurate and enable a higher hit probability in the direct fire mode out to 100 meters. Also, round range is lobbed to twice LV. This has been achieved by a combination of improved propellant and aerodynamics, allowing these distances to be achieved with only marginal increases in recoil.
RHEINMETALL
Rheinmetall’s work on the SCAR program has been via a subcontract with FN Herstal. Bohm said, “Some customers want to put illumination down range. Others, like USSOCOM, want flat trajectories to reduce the time of flight for fighting in urban terrain against highly mobile targets.” Production rounds will be delivered in 2009, although testing has been going on since 2007. Initial work in MV has focused on highexplosive dual purpose (HEDP) and training rounds with air burst munitions (ABM) being added to the roadmap. Bohm said that Rheinmetall was developing ABM technology across all 40 mm velocities.
Rheinmetall has adopted an off-the-shelf approach to MV. Bohm explained, “We are using our standard, off-the-shelf, high velocity warheads from our existing range, so the whole family is there already.” This gives the rounds a 250-gram warhead as opposed to a typical warhead from the company LV range, which weighs 180 grams. This has been matched with a different propulsion system, which in testing has achieved ranges of 600–800 meters. Bohm said, “You hear a lot about increasing the firing distance with 40 mm MV. That’s true. That is something you can do with some, but not all 40 mm launchers. There are some launchers that can’t take higher recoil to fire up to 700–800 meters. We have teamed up with the companies who are developing new launchers to make sure that [our MV] system is the most flexible solution.”
He adds that ensuring the launcher can cope with the recoil forces is only part of the issue. “There has always been a question mark as far as the effect of recoil forces on thermal sights. There is more testing needed to say that it works, but as far as the launcher is concerned, it works.”
According to Bohm, Rheinmetall’s interest in MV was “originally sparked by a Swedish squad support weapon program over six years ago by the FMV [Sweden’s Defense Materiel Administration] to look at longer range solutions.” Bohm also said that Rheinmetall was working with USSOCOM on other LV 40 mm projects, including tactical marking and HEDP rounds.
Currently fielded U.S. projectiles are formed by crimping the warhead to the cartridge case in three places. Bohm explained that Rheinmetall sees this as a design weakness. “You have a lot of pressure. With crimping, you don’t have a constant pressure curve, and that means the projectile is not as precise as it could be.” Instead, Rheinmetall has adopted a screw-in solution across all their grenades in low, medium and high velocity. Bohm said, “We don’t crimp our projectiles; we screw them together, and we reach a very, very tough pressure curve.”
During testing of rounds at different temperatures, the company found different points of impact among crimped rounds, affecting standard deviation. At 100 meters range in direct fire mode, the system was accurate at 21 degrees Celsius, but at 63 degrees and minus 35 degrees, the system was off by minus 60–140 centimeters and minus 30–90 centimeters, respectively. In contrast, screw-in designs fired at the same temperatures had a standard deviation of less than 50 centimeters. In addition to improving range and lethality, Rheinmetall is working with the DoD on a number of other projects.
Working with the U.S. Marine Corps and Cyalume, Rheinmetall has also developed a green ammunition concept for training solution for 40 mm grenades, which combine the ability to train at night, mimicking the effect of tracer, while eliminating the possibility of unexploded ordnance and range fires, as well as generating significant cost saving. Rheinmetall’s solution is the luminescent training projectile (LTP), which has been qualified and is in service as the 40 mm x 53 MK281 Mod 1 high velocity round. It uses cold light technology to mimic the effect of tracer with the duration of the light emitted down to the user’s choice but not less than 20 seconds. The round has the same trajectory as real rounds, with the light being viewed using standard night vision equipment at night.
Two production lines have been established in Germany for training ammunition, but the company has also invested in two more sites in the United States for the Marine Corps.
The same LTP technology has been adopted for the XM1110 night practice round, the Mk312 tactical marking round and XM11490 less lethal round, all of which are low velocity 40 mm rounds.
Rheinmetall has also been funded by the Marine Corps to produce an MK281 Mod 0 cartridge. The round is an insensitive munition, which uses a propellant fill mix that turns to liquid when heated to high temperatures, preventing accidental discharge.
The U.S. Army has yet to pursue the fielding of medium velocity 40 mm grenades, according to Chris Grassano, project manager, Maneuver Ammunition Systems. “The Infantry School is always interested in seeing new things. They haven’t come to us with any requirements for advancing capabilities with new technology or a product improvement type of activity on these munitions, but if someone comes along and shows the Army a new capability, that may change.”
MEI
Florida-based Martin Electronics Inc. (MEI) has been working on an MV solution. The immediate catalyst for the development of the firm’s product line has seen interest from the British Army, keen to field a replacement capability for platoon-level 51 mm mortars, which have now been retired. Matt Eckel, director of business development, MEI, said, “That was the inspiration. We knew everyone in principle, wanted something that went further, lighter and cheaper, but we really had to wait for the requirement to come first.”
MEI’s work on what has become its Mercury HEDP round began in earnest in 2004. At that time, MEI was working with Milkor USA’s M32 Striker grenade launcher in support of a Marine Corps urgent needs requirement, achieving ranges of over 1,000 meters. MEI had developed MV technology but had hitherto lacked a suitable soldier-level firing platform, due to recoil effects on the shooter and the M203’s inability to handle higher chamber pressures. From this experience a dialed down solution was evolved, suitable for underbarrel grenade launchers but with extended range out to 800 meters. Eckel said, “We used a patented cartridge case system that we’ve also used in our Hellhound low velocity rounds. This allows more propellant to be used than the standard U.S. round, which really closes down standard deviation. It was, however, more than just a propellant solution; otherwise everyone would be able to do it.”
In addition, MEI has developed its own innovations in both aerodynamics and payloads resulting in a 25 percent increase in explosive fill over current rounds, also working with Chemring Defence UK Ltd., whose parent company Chemring Group PLC subsequently acquired MEI during the summer. Eckel said, “We have been working with them for a number of years. There is no transfer of technology; we send the ‘truck’ and they put their fill in it. We now have a suite of rounds—high explosive, training, marking, flare and red phosphorus—that are far past the concept phase and have been demonstrated successfully over and over again.”
In addition to improved range, terminal effects have also been enhanced and optimized for urban operations. Eckel said, “Our explosive pattern is a sleeve of fragmentation. This is big development for urban combat. A lot of guys now are shooting down alleys and across the street, not lobbing grenades to 400 meters. Current [M433] rounds have a cup at their rear. If you shoot at something closer than 125 feet, you will have casualty grade fragmentation coming right back at you. Our fragmentation pattern, however, goes out and to the side, and the fragments are bigger and with more explosive effect. We use an aluminium base, which minimizes the back blast.”
The increased velocity needed to achieve longer ranges also means the trajectory is flatter. At 100 meters, MEI has found that a man-sized target can be accurately targeted using a standard rifle sight.
Eckel explained that they have also undertaken a lengthy testing process of current grenade launchers to ensure physical compatibility with higher pressure rounds. The most recent tests included a series of five round volleys, which took place in late May in Salisbury Plain for the U.K. MoD. These were shot using an underslung H&K AG36/XM320 from a fixed position. Eckel said, “That was a highly successful test. We used mostly marking, red phosphorous marker, smoke and illumination. We weren’t cleared for HE so we made a fuzed, inert round so everyone could still hear the fuze go off when it smacked against the target.” The current fuze on the U.K. program is a self-destruct fuze. “That is not yet a requirement here, but nonetheless all our rounds are built to a double specification.” Demonstrations in the United States have largely taken place at MEI’s own facilities.
Formal qualification of the MEI MV round is now being pursued in the United States. Eckel said, “You need a sponsor to do that, and that is what we are looking for now.”
Arcus Co.’s anti-diver high explosive grenade AR 476 M1/M2 is currently in the process of formal qualification with five NATO navies, with a number of special forces already operating the system, according to Georgi Bankov, marketing director at Arcus. The grenade, fired from standard underbarrel and handheld grenade launchers, has a range of up to 400 meters and arms from 10–40 meters. When it hits the water, detonation of its high explosive warhead is delayed for three seconds with a resulting shock wave of 10 atmospheres in a 12-meter radius, sufficient to kill or incapacitate a diver, and a further shock and disorientation effect of three atmospheres out to a 30-meter radius.
The company’s “bouncing grenade” range, comprising of the XR and AR 466 ABHE/FRAG-SD rounds, are now in service with Bulgarian and French special forces, with the U.S. Army evaluating them at Arcus’ own range in Bulgaria, in late 2007. The round’s fuze ejects the grenade’s warhead, depending on the round’s trajectory, 0.5–1.5 meters before detonation, with trajectory giving a defeat radius of 7 meters against standing and up to 3.5 meters against prone and entrenched targets. French forces operate a modified version designed to allow greater effectiveness when fired through windows. All rounds have a self-destruction backup after 14–19 seconds.
The firm has recently completed work on a new propulsion system for its 40 by 46 mm fragmentation and smoke ammunition, which extends maximum range by 50 percent to 600 meters, while retaining a recoil energy of less than 40J, sufficient to be used in current underbarrel and stand-alone grenade launchers, although sights would have to be recalibrated to deal with the extra range. The system has the same form factor as current grenades and is denoted with the prefix “X” rather than “A” in the company’s designation.
Singapore ST Kinetics has a wide range of 40 mm solutions, including its most advanced round, the LV S403 ABM part of the overall ABM Systems combined with the company’s Picatinnymounted fire control system, which programs the round fuze only once the round has left the barrel—arming itself at between 14 and 28 meters and utilizes either a self-destruct programmable time or point detonation fuze. Work on a medium velocity solution has begun recently according to Vincent Tang, assistant vice president, Kinetics Marketing Group, Singapore Technologies Kinetics.
The company has recently begun now scoping requirement via a feasibility study focusing on an improved propulsion solution with the goal of testing prototype MV rounds by the end of 2009. ♦