Innovative: Nammo’s New M72 FFE—An Achievement in Perfect Countermass Balance

Innovative: Nammo’s New M72 FFE—An Achievement in Perfect Countermass Balance

ABOVE: Nammo’s liquid countermass maintains uniform viscosity across all war fighting environmental temperature ranges. The atomized cloud formed by mass ejection is relatively small and rapidly dissipates from the air in seconds.

When new technology emerges, we all hear descriptive terms used like “state-of-the-art,” “revolutionary” and “decisive.” These terms attempt to describe a technology that clearly separates it from its competitors. None of these terms adequately describes Nammo’s M72 FFE (Fire from Enclosure). Why not? Because the M72 FFE provides a “divisive” advancement in countermass propulsion capability and warhead effectiveness.

Founded in 1960 by Franz Talley with U.S. headquarters in Mesa, Arizona, the Nammo Talley Corporation has been an innovator in the development of aircrew escape systems, automobile airbag components, shoulder-fired weapons systems and other key propellant-loaded devices. Specializing in the design, development and manufacture of ammunition and energetic material solutions, Nammo is a world-class provider of ammunition, rocket motors and demilitarization services for both military and civilian customers.

Looking outwardly similar to the Vietnam vintage M72 LAW (Light Anti-armor Weapon), Nammo’s M72 FFE is not an improved version of the M72 LAW. Then why the M72 designation one might ask? Think of the M72 as a “family” of munitions that has shared some design and component features over several different generations of configuration. As the field of Materials Science evolved, so did the options for new launcher and warhead designs. New modeling capabilities additionally enhanced Nammo’s design lanes facilitating technology breakthroughs in fuzing, explosives and propellants. In turn, this allowed Nammo to tailor M72 performance to the warfighter’s operational needs. Perhaps a quick historical review might be helpful to establish a better understanding of why the M72 FFE offers a significant advancement in recoilless shoulder-fired weapons.

When the M72 FFE is extended for firing, its length totals only 38.6 inches with a shoulder-balanced center of gravity making it easily held and aimed.

There Is a Difference Between Recoilless Rifles, Launchers and Guns

The terms “recoilless rifle,” “recoilless launcher” and “recoilless gun” are usually synoptic to most people. All three represent a type of lightweight artillery system configured into a man-portable launcher that ejects some form of countermass (such as propellant back blast) from the rear of the weapon when fired. This countermass ejection subsequently serves to counteract most of the weapon’s recoil, while at the same time creating forward propulsion for the projectile. Employing Newton’s 3rd Law of Motion, the simple process of equal and opposing forces reacting against one another, eliminates the need for massive recoil-absorbing devices associated with conventional cannons and artillery pieces. The result is a thin-walled, lightweight, launch barrel that launches a relatively large projectile.

While recoilless rifles, recoilless launchers and recoilless guns appear outwardly similar, there are some discrete technical differences. Recoilless rifles differ from recoilless launchers and recoilless guns. Recoilless rifles use ammunition that resembles conventional metallic-cased ammunition (only with vents perforating the cartridge casings), and they have rifled barrels that fire spin-stabilized projectiles. Recoilless launchers and recoilless guns are smoothbore variants that fire fin-stabilized rockets or fin-stabilized projectiles. This important distinction between spin-stabilized and fin-stabilized projectiles is often lost in discussion. Even though the launchers and the rounds they fire are different, they’re many times all mistakenly called recoilless rifles.

There is another key distinction between recoilless rifles, launchers and guns. A recoilless launcher fires a tube-launched, fin-stabilized rocket that employs a recoilless rocket launch principle. A recoilless rifle and recoilless gun both fire recoilless shells that use conventional gun propellant that often shoots fin-stabilized ballistic projectiles. Therefore, the significant difference (whether man-portable or hard-mounted) is that the projectile of the recoilless rifle or gun is initially launched using conventional propellant (a form of modern smokeless gunpowder) rather than a rocket motor.

A second point is that countermass recoil compensation in recoilless rifles and guns significantly reduces their effective range as compared to recoilless rocket launchers. While some recoilless gun variants utilize rocket-assisted rounds to extend the effective range, the projectile is still ejected from the gun barrel by first firing a gunpowder propellant charge. Once the projectile has left the launch tube, the rocket motor ignites and burns to drive it downrange. So, in general terms, the tradeoff for greatly diminished recoil in a recoilless rifle or gun (and ease of man-carried portability) is reduced range. That said, it must be remembered that range is based on projectile initial angular rate and time of flight (muzzle velocity and aerodynamic drag).

Weighing in at a mere 12.9 pounds with a collapsed carry length of 32 inches, Nammo’s M72 FFE is easily slung across one’s back or shoulder.

How Does Countermass Propulsion Work?

Today’s recoilless launchers, rifles and guns all operate by ejecting some form of countermass from the rear of the gun tube to counter (offset) the projectile’s forward motion upon firing, but this is not a new concept. The concept was originally developed by U.S. Navy Commander Cleland Davis preceding World War I. Davis attached two like guns at their breech ends, creating a double-ended gun. By firing both breech-end to breech-end guns loaded with projectiles of similar weight at the same instant, the recoil cancelled itself and countermass propulsion was operationally born.

In the Davis gun principle, the weighted mass fired from the rearward-aiming gun provided the countermass to the forward-aiming gun, mitigating the gun’s recoil. While Davis established the countermass propulsion concept in firearms, his invention had some serious design flaws. In view of the significant mechanical stresses applied to the midpoint joint of the two breech-joined guns, and the fact that the gun(s) fired in both directions at the same time (one towards the enemy and one 180 degrees to the rear), the gun was as dangerous to the good guys behind the gun as it was to the bad guys. Additionally, the duplicity of two joined guns made the weapon heavy (duplicity always adds weight) requiring it to be hard-mounted. Thus, the countermass concept languished further serious development in firearms until the recoilless rifle (spin-stabilized projectile) and bazooka (fin-stabilized rocket) were perfected about two decades later.

Today’s most common gun-launch countermass propulsion system involves venting a measured portion of the weapon’s propellant gas to the rear of the launch tube. In turn, this generates forward-directed momentum accelerating the projectile to muzzle velocities that are nearly equal to the rearward momentum of the expelled gasses. These equal and opposite momentums pushing against one another eliminate most of the gun’s felt recoil. Additionally, this simple countermass recoil mitigation process eliminates the need for hefty gun barrels, complex recoil dampening systems (as in artillery systems) and heavy gun mounts. It is virtually impossible for most countermass systems to achieve complete balance between the two opposing (rear and forward) competing forces, so recoil, of some degree, is usually present. However, Nammo’s M72 FFE design possesses a unique countermass balance making it truly recoilless.

The M72 FFE is offered in two identical weight 66mm warheads, the M72 E8 Anti-armor and the M72 E10 Anti-Structure Munition (ASM). Both warheads possess dual safe fuzes and weigh 3 ¼ pounds.

Countermass Back-Blast Mitigation

As previously discussed, countermass physics requires venting high-velocity propellant gases out the rear of the launch/gun tube. This results in a veracious back blast. No matter how tame Hollywood depicts their firing, these systems are not suited for firing inside confined spaces. Countermass propulsion systems expel an extremely fast-pulsed, obnoxiously loud, pressure wave rearward. The back blast is also ferociously destructive because of its energy and velocity. You do not want to be located anywhere behind a conventional countermass system much less inside a confined space when it’s fired. Many a soldier has lost an eardrum from exposure to a single firing. The design challenge has been to significantly reduce or eliminate countermass propulsion back blast, but how?

During the early 1980s two Naval Research Laboratory (NRL) engineers patented a new countermass ejection mitigation technology that used a powdered bismuth metal slug of comparative weight to the projectile [Why bismuth? Bismuth has a specific gravity close to lead but it’s environmentally friendly—lead is not]. They located the powdered bismuth slug just behind the propellant charge opposite of the projectile to mitigate the back-blast effects. When fired, the frangible bismuth countermass slug both countered the recoil and mitigated much of the effects of the back blast, allowing its limited use inside an enclosure. Even so, the powdered metal ejected at high velocity and was a “sandblast” eye and flesh hazard to anyone behind the gun.

That evolved to the use of a countermass slug formed from shredded plastic. When expelled, aerodynamic drag (resistance) quickly slowed the shredded plastic countermass rendering it harmless within a few yards from the rear of the barrel. Even so, the countermass back blast contained shredded plastic that posed an identifiable plastic confetti cloud signature behind the shooter when fired, and it still didn’t acceptably reduce the weapon’s report.

Fast forward—resulting from the Middle East Wars, the U.S. Marine Corps promulgated a requirement to be able to fire a man-carried M72 LAW-sized countermass weapon from inside a room-size enclosure 12x15x7 feet. Nammo weapon design engineers stepped up to the plate. The original M72 LAW (your father’s LAW from the Vietnam War era) was a tube-launched, single-shot recoilless rocket launcher that could not be fired from inside an enclosure without causing serious back-blast damage to both the shooter and the enclosure. In creating the M72 FFE, Nammo engineers took a new path to the material they used in the countermass. They developed a non-combustible, environmentally friendly liquid countermass—absolutely brilliant! With a 10-year shelf life (actually capable of much longer), Nammo’s liquid countermass formula is proprietary. However, its viscosity and feel are similar to radiator anti-freeze (in diluted form), and its performance is stable in all war fighting operational environments from desert heat to artic freeze.

Nammo’s M72 FFE Liquid Countermass Technology

Nammo’s M72 FFE liquid countermass technology achieves many previously unattainable capabilities. First, its back-blast countermass ejection is all but harmless, even at close exposures. When the M72 FFE is fired, the liquid countermass is atomized by the high-pressure gases generated by the propellant burn. The atomized liquid is ejected from the rear of the gun tube in the form of a suspended particulate cloud. This vastly reduces its overpressure, flash and report. In turn, this renders it nearly harmless to the gunner and others close by, to the point that only single hearing protection (ear plugs) is required by the gunner for up to 8 shots per day when firing from an enclosure as small as 12x15x7 feet. Nammo also advertises that no hearing protection is required for a single shot per day—a very impressive decibel reduction that meets OSHA requirements.

Second, because Nammo’s liquid countermass material is dense and has uniform viscosity across the operational temperature range, the atomized cloud formed by mass ejection is relatively small, and it rapidly dissipates from the air in seconds. This makes both day and night visual identification of the shooter’s location more difficult. The mass ejection viscosity also serves to dampen (suppress) the weapon’s sound signature, making it even more difficult to locate from the receiving end.

Third, Nammo’s M72 FFE is user friendly and almost marine-proof because the 66mm projectile, propellant charge and liquid countermass come prepackaged inside a waterproof telescoping launcher. The launcher is made up of two tubes, one inside the other with waterproof endcaps. There’s nothing to load. You just extend the tube and shoot. After firing, the tube is discarded.

Unlike the LAW, the FFE is a tube-launched, single-shot recoilless gun that fires a 66mm fin-stabilized ballistic projectile (not a rocket). The M72 FFE’s total weight is 12.9 pounds. With a collapsed carry length of 32 inches, it fits easily inside a rucksack or is slung across one’s back or shoulder.

When the M72 FFE is extended for firing, its length totals only 38.6 inches with a shoulder-balanced center of gravity, making it easily held and aimed. The tube extension process is uncomplicated and intuitive. The inner tube telescopes rearward, guided by the channel assembly which rides in an alignment slot. When the two tubes are fully extended, a detent lever moves under the trigger assembly in the outer tube. This locks the two tubes in the extended position and also cocks (arms) the weapon. Similar to LAW configuration, the FFE’s outer tube contains the trigger, the arming handle, plus the front and rear sights. However, the FFE also has the addition of a Picatinny top rail should the warfighter wish to add his own aiming or illumination devices to the weapon. Note: If the M72 FFE is collapsed back into its original carry configuration, the weapon is no longer watertight.

The M72 FFE’s propellant ignition employs a reliable, mechanical striker-type percussion cap, (uses a standard large rifle primer) firing mechanism. When fired, the propellant charge completely combusts by the time the projectile leaves the launch tube. At this point, eight fins spring out from the base of the projectile, stabilizing the projectile’s ballistic flight path. The projectile itself has an electro-mechanically fuzed warhead. The warhead’s safe and arming (S&A) distance envelope is not less than 12 meters and no more than 18 meters. This arming standoff provides adequate shooter safety for near-target engagement and emergent engagement at downrange minimums. Further, it has two identical weight warheads to choose from, the M72 E8 Anti-armor and the M72 E10 Anti-Structure Munition (ASM). Both warheads are configured with dual safe fuzes, and they both weigh in at 3 ¼ pounds so aiming and flight ballistics are identical.

The ASM warhead uniquely incorporates a self-discriminating fuze that increases the munition’s ability to defeat a wider variety of structural targets by detonating in either a fast or delay mode based on target construction. Therefore, the warhead’s self-discriminating fuze automatically reacts to the target material it contacts providing optimized, warhead payload penetration. This provides warfighters the ability to confidently engage and successfully defeat a wider variety of targets using a single warhead.

For training purposes, Nammo still offers its standard 21mm trainer rocket and launcher. The training launcher has a 21mm barrel permanently fastened inside the larger M72 launcher and is designed to provide the warfighter the realistic feel of actually firing an M72. The trainer is reusable and can be reloaded and fired hundreds of times, significantly reducing training costs.

Finally, the USMC is conducting M72 FFE suitability and acceptance testing that is expected to successfully conclude by the end of 2018. They have already earmarked funding for the first M72 FFE lot procurement with a mix of anti-armor and anti-structure warheads. The USMC intends to have the M72 FFE in war-fighting operational service by mid-2019. There are many M72 FFE attributes that make it a divisive weapon on the battlefield, but there is one that truly makes it great: It’s made in America by Americans for United States Marines.