<XMP><BODY></xmp> MBIL -a new airburst Infantry weapon

Added 29-4-03
Updated 10-9-10

Marines examine homemade Iraqi multi-barrel rocket weapons

Below I suggest some ideas for a lightweight recoilless weapon using programmable airburst technology.

The basic RLGL weapon would have two side by side 40mm barrels or four 40mm barrels in a 2x2 configuration. These would be combined with a ranging laser, fire control unit/round programmer, handgrips, shoulder rest etc. These barrels are rifled and can be easily muzzle loaded by the gunner. Main ammunition for these barrels are 40mm programmable-fused anti-personnel rockets or rifle-hand grenades mounted on booster units. Most of the other rounds described below can also be fired. The same rounds can also be used in the single tube mounted above a rifle that Ralph Zumbro suggests.

Operation of the RGCL would be simple. The target would be lased and the round programmed. A simple LED display would indicate if the muzzle needed to be raised and when it is at the correct elevation. Lateral movement of a thumb-operated D-pad would select fuse mode (eg Air-burst, Point, Delay or Stand-off distance for HEAT rounds). Moving the pad up and down would select options such as detonate before or after the lased range or time of delay. A programmed timing mechanism combined with an accelerometer in the projectiles would detonate the round at the desired distance.

One concept I entertained was a pair of complimentary launchers. One system would be multi-barreled and fire 40mm rounds. The other would be single barreled and resemble a RPG-7 with a programmable fusing fire control system added. This could fire air-burst 40mm rounds and larger overcalibre RPG-7 rounds. A platoon would field a mix of single and multi-barrel systems.

My one reservation about going the RPG-7 route is that the standard anti-personel round, the 40mm OG-7v weighs 2kg, is nearly as long as a anti-tank RPG rocket and its explosive content of c200gm may have too large an effect area. In certain conditions that may be a hazard to non-combatants, friendly troops or even the user.

Thinking on this further, I researched the medium velocity (MV) 40mm grenades that did not exist when I first wrote the MBIL article.

Many medium velocity 40mm grenades have double the explosive fill of standard low velocity (LV) 40mm (86g of HE compared with 32-45g). This gives them the same explosive capacity as many hand grenades. Compared to the LV 40mm it is claimed they have 45% more fragmentation effect and I've seen one type claim twice the casualty radius of a M433, which seems credible.

Muzzle velocity is also higher at c110m/s vs 76m/s and sectional density will be better giving slower velocity loss. MV rounds are claimed to have an accuracy of 7 metres at 800m and to have reached 950m. Perhaps more significant is that these rounds can be fired directly at targets out to about 300m. Therefore at most combat ranges exact range and holdover are not a concern for the operator.

Basically the medium velocity rounds offer shorter flight time, flatter trajectory and bigger effect area, all of which add up to a higher hit probability. Used in repeating weapons like the M32 missed shots can be rapidly corrected and rounds walked onto small targets such as loopholes.

So something like the M32 with MV ammo may meet many of our needs. Systems to add programmable airburst capability to LV 40mm grenades are already being offered so it is very likely this capability will be added to MV grenades. A semi-automatic weapon would reduce felt recoil and a drum magazine or detachable cylinder would be preferable. Such a weapon might look like a shorter, lighter version of the Chinese 35mm launcher.

To give the grenadier a capability against bunkers and armour a M32-type MV grenade launcher with programmable fusing fire control may also include a mounting bracket for a weapon along the lines of the Brunswick RAW.

While the RAW used a ball round to launch it, it didn’t use this for propulsive force: it just tapped off some of the propellant gas to work the firing pin. A RAW with an alternated ignition system, such as electrical should be simple enough and would allow launch from a bracket on the M32. I have suggested elsewhere a version of the RAW based on the DGL and such a configuration would allow mounting on rifles, grenade lauchers or even independent use.

Unlike most missiles, RAW used its rocket motor both for propulsion and to oppose gravity, so had an effectively flat trajectory out to 200m. Within this range the shooter did not have to worry about hold-over or exact range to target. The RAW was a soft launch system, so could be fired from confined spaces such as the interior of buildings. It accelerated to 173m/s at 200m and took 1.9 sec to reach that range. Calibre was 140mm and the missile seems to have been under 12” long, so not too bulky for a soldier to carry several.

An updated RAW launched from a M32 would be really useful. Personally I'd like to see that time of flight trimmed down to give the enemy less time to dodge or deploy countermeasures. This would also make the missile more useful against fast moving vehicles or slow moving aircraft. That may mean a more powerful motor and/or a smaller warhead, but a 105mm warhead would still be superior to many infantry antitank systems.

The original RAW warhead was a HESH that could blow a 36cm wide hole through 20cm of double reinforced concrete. There was also a “flying claymore” with about a kilo of HE and tungsten fragments that potentially could take out a whole squad. Anti-tank rounds with HEAT or EFP warheads were also tested, and interesting is that these used a laser proximity fuse for correct stand-off. Turn off the fuse and the round was an effective HE round.

MBIL: The Airburst Weapon The Infantry Really Needs

In a previous article I’ve looked at the design strategy of the OICW, aka the XM29. The most recent articles that I’ve seen on this weapon seem to have dropped the rather unlikely idea that the system will be effective to 1000m.

A programmable airburst munition does seem to be a good idea, but one can’t help but wonder just how much more lethal a 20mm grenade will be over the current 40mm rounds? Despite the claims in the promotional articles, one suspects the real answer is probably “not very much”. A photo here shows fragments hitting the ground 2.5m from an airburst. The effective radius may be greater, but it is unlikely to be significantly more than the 5m radius of the 40mm

In the previous article I pointed out that an airburst round for the 40x53mm AGLs already exists, so creating a 40x46mm version for weapons such as the M203 and revolver grenade launchers should be possible. ST Kinetics of Singapore offers a kit that will convert any 40x53mm AGL to fire such rounds.

PDF on the programmed 40x53mmSR weapon

The problem with the current 40x46mm weapons, however, is that they are low velocity rounds (71-79m/s), so have a very curved trajectory. This means that in practice it is very difficult to get a round within 5m of the desired target.

My proposal is to take the programmable-fuse developed for the 20mm OICW round and mount it in a larger projectile. To use this requires a fire control system and a compatible weapon to mount it on.

My suggestion is to combine various technologies to create a lightweight recoilless grenade launcher (RLGL) capable of firing larger air-burst rounds that will fly faster, further and flatter.

The Round.

For an idea of what the larger projectile I propose mounting the OICW programmable fuse in would be like let us consider the various muzzle-launched rifle grenades in current use. These give us some idea of a practical weight and bulk for the rounds.

Rifle Grenades

The rounds might also resemble 51mm mortar rounds, and some components of these might prove useful in constructing this round.

51mm Mortar and Rounds.

Most rifle grenades have a destructive capability of similar levels to the M61 and M67 hand grenades. These contain about 6oz of Comp B and have a casualty radius of 10-15m, so one RLGL shell will cover about nine times the ground area that a 40mm grenade cartridge would.

Some models of rifle-grenade already have rocket-assistance. Since the projectile I’m going to propose will not need to fit over a rifle barrel, there is room inside a more powerful motor to give a flatter trajectory. The mechanism by which the OICW fuse determines range involves counting rotations, so our projectile will need to be spin stabilised and will probably not be finned. That will reduce the tendency of the round to “weathercock” in cross winds. In fact it is more likely to resemble a conventional shell in shape, even if it contains a rocket motor.

To use the existing OICW fusing a grenade will need to be spin stabilized. Israel Military Industries have developed a rifle grenade that has a programmable time delay fuse that is set by a fire control system. It should be possible to create a recoiless launcher fired projectile that does not need to be spun-based on a timing mechanism. I’m not certain how accurate this would be in strong head or tail winds. The solution is probably to combine a timing mechanism with an accelerometer so the firing mechanism can determine if it has travelled the required range for detonation. Spin-stabilization may be the better system for grenade-sized projectiles anyway.

My initial feeling was to have an overcalibre round, not that dissimilar to some of those fired by the WW2 German Schiessbecher.


Like the Schiessbecher rounds the shell is a spin-stabilised overcalibre design. Unlike the Schiessbecher the round will be fired by a larger charge and may have its own sustainer rocket, so will fly further and flatter. The round also has the advantages of programmed air-burst fusing, of course.

Such a projectile would be shaped rather like a finless rifle grenade or a tall toadstool. The “stem” would fit into a rifled barrel of 30-40mm calibre while the warhead would be of a large calibre and remain outside. Since the round is not intended as an anti-tank weapon the calibre of the projectile can be kept under 51mm, which will reduce drag and improve exterior ballistics.

Stan Crist pointed out to me that the US military doesn’t like overcalibre projectiles, and this made me realise that there was no real reason why this round needed to be overcalibre. In fact, most commercially available rifle-grenades are of 37-40mm calibre. Using a 40mm round would allow existing components and tools to be used for this weapon.

Projectile weight would be under 1¾ to 2 lbs, so quite a few rounds could be carried.

The 82mm SMAW has a launch velocity of 270m/s, so it is not unreasonable to expect such performance from our smaller-scale RLGL. Interestingly, this gives us a similar muzzle velocity to that of the Mk-19 AGL (240m/s), but with a lighter weapon and a more destructive round.

Many nations field 40mm anti-personnel rounds for the RPG-7. Quoted velocities are around 150m/s, which seems a little modest compared to other heavier RPG rounds. Range is given as 950-1800m. Warhead size is described as 210gm-1.1kg, although the smaller figure may be the explosive content and the larger the total weight including fragments. Lethal radius is given as more than 25m.

The Launcher.

The sighting and fire control system needed for the launcher would be the same as has already been developed for the OICW with just a few changes to the software to allow for the different projectile.

The rounds I propose could be fired from weapons such as the 3BT or DP-64 if fitted with a fire control system (FCS) capable of programming the rounds for airburst.
Arpad 600 35mm launcher

One idea is to launch such projectiles from weapons something like the Swiss Arpad 600 (left). On firing the barrel recoiled out of the rear of the weapon a distance of 14"/35cm, controlled by a hydro-pneumatic buffer. There was no backblast and the 35mm 167gm projectile was propelled at 600m/s. Since the round took only a second to reach 500m the weapon had considerable potential against moving targets. It was intended for destroying point ojectives such as machingun nests, light vehicles and helicopters. The launcher weighed 6.8kgs and the rounds were light so 20-30 could be carried by the firer. The HE round contained 45gm and had considerably greater range and accuracy than a conventional rifle-grenade.

Arpad 600
Arpad with piston recoiling

I think the Arpad loaded from the breach, which I feel is not so desireable for a weapon of this type. The basic design could possibly be adapted to magazine-feed.

My preference, however, is that such grenades be launched from a lightweight, muzzle-loaded recoilless launcher fitted with a fire control system.

A single-shot launcher would work well, since the operator can easily reload it himself but a double or multiple-barrelled weapon is also possible with such small-calibre rockets. A double-barrelled launcher may look like the weapon below from the videogame “Halo(below), or this existing Chinese weapon.

We might see an evolutionary approach to developement of this weapon system. The initial weapon would be a single shot launcher firing a “dumb” impact detonated projectile. This would increase the capabilities of units within a short time frame. Developement can then be applied to the perfection of a multi-shot launcher and one with a fire control system.

A singleshot weapon with dumb rounds would be useful. A single-shot weapon with programmable rounds or a multi-shot weapon with dumb rounds would be even more useful, and a multi-shot programmable weapon would be a great improvement over existing systems.

One possible design for a launcher is to have what I call a “recoilless pepperbox”. At the front of the weapon is a cluster of three to seven muzzle-loading barrels. These rotate so that the one being fired aligns with an exhaust tube that passes over the operator’s shoulder.

For want of a better term I call this version of the RLGL the Multi-Barrelled Infantry Launcher (MBIL).

It is possible that the MBIL will serve alongside a single-barreled version of the RLGL that resembles an RPG-7. While the MBIL has repeat-shot capability a single-tube weapon is more suited to firing large over-calibre rounds more suited to anti-armour and demolition roles. Currently an RPG gunner can carry only two or three large rockets. Equiping him with a Single Barrel Infantry Launcher (SBIL) allows him to also carry several 40mm anti-personnel rockets allowing him to save the larger rounds for suitable targets. Possibly the SBIL could fire captured RPG ammo. Different squads within a platoon will either have MBIL or SBIL.

The MBIL is not intended to replace the section anti-tank weapon but be an alternative to the XM29 and low-velocity 40mm grenade launchers. The flatter trajectory and higher velocity will make it easier to place the round close to the intended target and the larger area of effect gives a greater margin for error and increased shock effect. Its capabilities also means that it can substitute for the platoon mortar in certain situations.

An interesting idea that has been proposed to me by my friend Ed Sackett is that barrel from which the round is fired should be disposable and could also serve as the shipping container –rather like the SMAW in reverse. To reload or change load you just attach a new barrel and round.

Crude impresion of what the MBIL might look like

The above illustration is a crude impression of what the MBIL might look like with overcalibre rounds. With full-calibre rounds the warheads would not be visible and the barrels might be loaded from a gate at the back of the cylinder. An alternate configuration might look a little like the Arwen 37 with an exhaust pipe. Possibly the cylinder could be placed behind the operator, though this might prevent firing from a prone position.

Revolver type MBIL

The exact form of recoilless mechanism that is used needs to be determined experimentally. The launcher may be a small recoilless gun (like the Panzerfaust) or pure rocket launcher (like the RPG-2), or a hybrid of the two (like the RPG-7).

In the above description I’ve assumed a rocket sustainer motor. The recoiling barrel idea of the Arpad is worth investigating for this weapon since the recoil forces that need to be managed are smaller than those for anti-tank weapons. Firing a projectile of a pound and a half will produce less reaction forces than an anti-tank rocket of 5 lbs+. Correctly designed the recoil movement of a piston could be used to rotate the barrel cluster and the mass of the system would help counterbalance that of the barrels.

During World War Two the Rhenmental-Borsig developed a system called “Hammer” or “Panzertodt” (tank-death). This used projectiles with a pear-shaped tail with propellant placed around the tail boon. The interface of the tail and barrel wall acted as a ventura without the need for a complicated machined structure. If I recall correctly this system worked rather well and some of the systems did see action before the war ended. Such a mechanism might have applications for the MBIL or other recoilless weapons, particularly disposable ones.

Ralph Zumbro: If the cocking lever of an M-16 were moved to one side or other, there would be nothing on top of the weapon to prevent mounting a 40mm-60mm tube that was long enough to exhaust over the trooper’s shoulder.

Attach the handle to the LEFT side of the bolt carrier and use a rubber sealing slit to crud-proof it. Put the battery for igniting the rocket inside the pistol grip. It’d be a special-issue weapon, of course, but a shortie would be a usable crew weapon

Such a weapon would be a good platform for RLGL rounds, and a useful supplement to the MBIL. There already exist variants of the M16 that omit the carrying handle and have a rail Interface along the top. I’ve even seen a version with a folding front sight. These upper rails are intended for sighting systems but could also be used to mount overbarrel launchers.

The operator could load this weapon himself if the forward section of the tube slid forwards like a M203. In fact the barrel of the M203 might be modified to this system by fitting a new breach section and trigger.

Types of Round.

The MBIL would be capable of firing a considerable variety of ammo and since the rounds are relatively compact it will be quite practical for the operator to carry several kinds if necessary. These pictures show soldiers solutions to carrying rifle grenades, and the same could be done for MBIL rounds.

Israeli Soldier with “Quiver” of rifle grenades on his back
Colombian soldier with rifle grenades in leg pouch (right)

Some of the suggested projectiles include:

Fragmentation-Air Burst

This will be the type of round that will probably be used the most. The warhead is designed to throw the fragments in a cylindrical rather than spherical pattern to reduce the minimum safe range and increase the weapon’s usefulness in close range combats. A larger version of the universal rounds described in the OICW article are also possible. This would give the option of fragments being spread in a radial or conical pattern.

Another possible round would be an EFP round fitted with a fragmentation sleeve and a splitter ring. On detonation this would throw fragments to the sides and ahead of the exploding round. By removing the splitter ring the round can project a penetrating slug for use against harder targets.

As well as programmable-rounds another avenue worth exploring is that of proximity fusing for RLGL rounds. One wonders if in a few years it might be possible to create a fuse that distinguishes between soldiers and scenery.


This round would be loaded with flechettes or buckshot and used for jungle fighting, CQB and other applications where the use of Frag-AB rounds would not be possible. A variant that discharges a cloud of CS/CN/OC is also possible.

The Israelis have the IMI ARG/AP-50, a form of “rifle grenade” that does not leave the muzzle but instead projects a cloud of flechettes. These have proved very useful for firing through chain-link fences erected to protect from RPGs. The round for an overcalibre MBIL could be along similar lines. The 53mm calibre round weighs 640gms and fires 160 flechettes in a 10 arc with a range of 50m. For other designs of RLGL the canister rounds are more likely to resemble large shotshells or those for the M203, but with increased capacity.

Such rounds will also see applications in the construction of booby traps or be used instead of Claymores.

The “reverse SMAW” configuration could also be used to fire canister loads, clouds of CS or large Flame cartridges, all of which enhance the close range capabilities of the launcher.


There may be applications for a simpler round without the programmable-fusing. This would have a simple impact fuse (possibly the same as the M68 or M433) and possibly have a small bounding charge in the nose to throw the grenade into the air just before detonation.

Ralph Zumbro: Could you simply create an electrically-ignited rocket motor that could be INSERTED in the launch cavity of most common rifle grenades, and give it long-range capability if fired outa that tube? Also, that sucker would have a nice range as an indirect fire weapon.

Such a simple add on unit would be a very cost-effective way to adapt 37-40mm rifle grenades for firing from the RLGL as dumb rounds. The rifle-hand grenade would be a prime candidate for adaption in this way.

Chemical/Anti-Riot Air Burst

This is similar to the frag-air burst round but constructed so that there is very little chance of producing lethal fragments. The warhead contains pellets of CS or some other non-lethal agent. The same basic design could be used for a screening smoke round.

White phosphorus.

Multipurpose round suitable for anti-personnel, incendiary and screening uses. Such rounds are very useful if fired against the firing slits of bunkers. This might be an adapted WP rifle hand grenade.


Used for stand-off attack against targets such as buildings and bunkers.


Using this round the MBIL has applications similar to those for the M202 Flash but without the need for a dedicated weapon.


The MBIL is not intended to be an anti-tank system but there may be applications for hollow charge rounds to give the weapon increased capability against soft-skinned and lightly armoured targets. These projectiles may be of a larger-calibre than the other rounds. That the MBIL round is spin-stabilised may make the HEAT round less effective but this may be offset partially by the weapon’s capability to use programmable-fusing to detonate the round at the optimum stand-off distance. Possibly the standard round for the RLGL will be a programmable HEDP offering HEAT and frag capability.

High Velocity.

There may also be applications for smaller-calibre high-velocity rounds that can be fired at fast-moving or distant targets.

Overcalibre Rounds

Although the RLGL is intended to fill a similar niche to the current M203 there is a temptation to give the weapon an increased anti-armour capability.

It may be possible to construct an overcalibre RPG-type round for the RLGL and MBIL. Use of a slipping ring would solve the effects of rifling. The weapon could then operate as either the section’s single-shot anti-tank weapon or a multiple shot grenade launcher.

A two or four barreled launcher can be loaded with either a single overcalibre rocket or several 40mm grenades. It may also be possible to load a grenade and an overcalibre rocket, although the grenade could not be fired until after the rocket has been launched, and there would be safeguards to ensure this.

Hollow-charge anti-tank rounds perform best if they are not spun, so some form of slipping ring needs to be included in the design. This is already a feature of HEAT rounds fired from recoilless rifles such as the Carl Gustav. An alternate system would have HEAT rounds with a tail that fits between the lands, while other types of round would have a system that engages the rifling. To allow fast loading and easy unloading the rifling band would not engage the rifling until the round is fired. Similar systems that only engage the rifling when the round is fired already exist for some mortars.

The “reverse SMAW” configuration that has already been suggested would solve most of these problems. The grenade would come in a shipping cylinder with a rifled interior that snaps onto the front of the exhaust tube and interfaces with the fire control unit. A recoilless version of the system described for the DGL, using a threaded spigot is a possible alternative. Larger rockets would have a smoothbore tube and the tail of the rocket would insert down the exhaust tube to give a shorter and better balanced weapon. Larger rockets can also be fired directly from their carrying container, as has been discussed under the Universal Launcher concept. Some types of larger rocket could also use programmable-fusing when fired from the launcher.

An alternate approach to integrate into this weapon the capability to fire larger rounds such a anti-tank or bunker defeat munitions is to mount a mounting bracket for the ULAW family of munitions above the 40mm barrels. This allows the ULAW to be fired with a more sophisticated sighting system. Being ULAW weapons these rounds also have the capability to be launched without using the RCGL launcher.The RCGL therefore either serves as an anti-tank weapon or a multishot high-velocity grenade launcher.

Another solution is not to bother and to accept that the RLGL is no more an anti-tank weapon than other anti-personnel grenade launchers such as the M203. (The RLGL would however be more effective against light armour and soft-skins such as technicals). If both anti-tank and anti-infantry capability is needed then it is quite possible for one man in the squad to operate the RLGL while others man anti-tank systems such as Javelin, AT-4 or ULAW. Issuing SBILs capable of firing overcalibre rounds alongside MBILs is another solution. In addition to anti-tank rounds the SBIL will also be provided with thermobaric and anti-bunker munitions.

The above gives some idea of how useful the MBIL will be.


Stan Crist: In the 1960s MBAssociates developed and marketed the Gyrojet rocket pistols and carbines. What is less widely known is that MBA also had plans to produce a larger-caliber, shoulder weapon that fired 30mm rockets with high-explosive warheads. With no recoil forces to contend with, the weapon was to be exceedingly lightweight -- a mere 2.9 lbs with empty 5-round magazine, and 6.9 lbs fully loaded. Max range of 3,100 meters.

The company called it a Hand-held Anti-personnel Shoulder Fired weapon, or HASF. It was somewhat similar in concept to what you and others have proposed for increasing offensive combat power of the infantry squad, in that launch tube sat atop the shooter's shoulder, with the rocket exhaust vented behind him.

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