Added 9-5-03
Updated 13-5-15

Disposable Grenade Launchers

DGL and Less Lethal Weapons.

It seems likely that we will see increasing use of Less-Lethal Weapons (LLW) by both military and police personnel. Disposable Grenade Launchers (DGLs) have a lot to offer for these applications. Currently LLW ammunition is offered in configurations that cannot be used in lethal weaponry and configurations that can. One approach requires a force to have a duplication of weapons with similar capabilities, for example 37mm and 40mm launchers. The other approach runs to the risk that in the heat of action lethal ammunition being used when LLW was intended. The DGL concept allows LLW ammunition to be of a distinctive and clearly identifiable form but can still be fired from any weapon or device with a Picantinny rail. For example, lethal grenades would be 40mm calibre and LLW ammunition 56mm.

Another useful capability of DGL for LLW rounds is that a variable velocity system could be incorporated in the launcher. Three or four captive piston cartridges would be in contact with the base of the projectile. For close ranges only one cartridge would be fired, ejecting the projectile at a relatively low velocity. For longer ranges multiples would be fired, desired range being set by a simple dial on the side of the launcher. This system would be very useful for kinetic energy impact LLW projectiles such as “beanbags” or putty rounds.

Disposable Grenade Launchers (DGL) are an idea that I have been pushing for some time, but I decided that it was time that the concept had a page of its own, and I have added a diagram. Disposable Grenade Launchers are a family of one-shot disposable munitions designed to fit to the Picantinny rail interface system of a rifle, shotgun or SMG. They can also be hand-fired, mounted in batteries or utilised in booby traps.

Recently I have learnt that during the SPIW trials AAI experimented with a similar idea.

“....AAI also proffered another grenade option, the DBCATA: Disposable Barrel and Cartridge Area Target Ammunition. The DBCATA allowed the 40mm grenade to act as its own launcher. While it would lead to a major reduction in weight, the DBCATA was considered prohibitively expensive. Essentially, you would be throwing a barrel away at each shot.”

It seems that it did not occur to AAI to use a spigot-based system which is surprising since successful spigot weapons date back to at least the Second World War, the most well known being the PIAT and Hedgehog. Post-war refinements of the spigot system have included the Belgium Fly-K mortar, used by the French as the TN-8111. This uses a captive piston system within the projectile for a flashless, low-noise launch.

The illustration gives the basic layout of a captive piston DGL with a fragmentation warhead. For clarity several features such as the ignition system and the hand-thrown fusing system have not been shown. A perforated plate to produce a hi-low pressure system could be added between the propellant charge and piston if necessary.

Key: EC=End Cap. Pis=Piston head Pr=Propellant F=Fuse G=Grenade OC=Outer casing RIS=Attachment rail for rail interface system FM =Firing Mechanism P=Post ST=Spigot tube

The launcher attaches to the rifle or another weapon by means of the rail on the outside. The handle of the firing mechanism folds down to arm the system and expose the trigger.

Ignition of the propellant (Pr) causes the piston head (Pis) to move down the spigot tube (ST) against the post/spigot end (P). The post has spiral channels cut or cast into it and these engage with studs at the base of the spigot tube, imparting spin stabilization for the grenade (G). The plastic end cap (EC) is pushed off as the round moves up the spigot. The outer casing (OC) functions only to protect the grenade when in transit and to prevent the firer's hand resting on a launching grenade. When the piston head reaches the end of the spigot tube it is arrested and this seals the propellant gases within the tube so launch is flashless and nearly noiseless. Such a system has already been used successfully in the FLY-K mortar.

The text below is from my grenade launcher article that originally appeared in G2mil and is on the Scrapboard at this page.

Several of my ideas have evolved since this was first written. Given the SPIW findings it may not be economical to use the same shells as used in 40x46mm rounds. These rounds also have a limited effect area and the DGL configuration may allow the use of heavier projectiles with a greater effective area.

DGLs probably can replace the M203, especially if they are issued alongside weapons such as the RLGL and the Blunderbuss.

Disposable Launchers fill the same role as rifle grenades: they give each man in the squad grenade projecting ability and are a supplement to the 40mm grenade gun, not a replacement. They offer several advantages over grenade guns and rifle grenades:

• Unlike rifle grenades they can be carried “ready to fire” and still allow the rifle to be used.
• When the launcher is not fitted the rifle is unencumbered and more responsive.
• Tubes can be built that fire 40x46mm cartridges, conventional and rocket-assisted rifle-grenades or hand-grenades. The charges used to propel the latter can be optimized for the projectile rather than just being a blank or ball round.
• They can use captive piston systems for low-noise flashless launch.
• DGL can fire rounds that cannot be launched from grenade guns.

Examples of rounds that cannot be fired from grenade guns include:

• Ring airfoil grenades: for flat-trajectory shooting of either riot control or explosive munitions.
• Multiple loadings: for example, an anti-ambush round consisting of a canister round and a ring-airfoil white-phosphorus grenade. Multiple loadings of M203-type rounds are also possible.
• An incendiary round based on the German Hafla DM 34.
• A cartridge flow-stream flamethrower.
• A flame capsule grenade containing thickened pyrotechnic agent (TPA).
• Multi-shot canister loading (either multiple barrel or superimposed). More on this idea on the MetalStorm page.
• Grapple and line.
• Underbarrel version of the Brunswick RAW.
• A 7-9 barrelled “volley gun”, each barrel loaded with several projectiles. This would offer a longer ranged alternative to canister with better penetration.

Other potential rounds include:

• Windscreen-penetrating round (detailed elsewhere).
• Depth-fused anti-swimmer projectiles.
• Door-buster rounds

DGLs loaded with OICW rounds may be possible but unless the rifle is fitted with a fuse-setting interfacer these will only function as impact-fused projectiles. A simple interface unit where the detonation range is manually selected could be fitted to a rifle or made part of the disposable unit.

It has been suggested to me that fired launchers should auto-eject from the rifle: this would be a good feature so long as this mechanism doesn’t operate when the launchers are being fired hand-held.

I have called these devices disposable: they should be cheap enough to be treated as disposable but for training purposes they may be capable of being reloaded several times.

A friend suggests an alternate strategy:

“These are a good enough idea that I suggest a small additional wrinkle: make two models.

M1 is a robust steel and alloy version that can be reloaded by the soldier. This is for economical training purposes.

M2 is a cheap plastic and fiberglass version, ideally w/ a break-apart feature that prevents it from ever being fired more than once. This is for advanced training and, esp., for war. If they’re disabled by firing, no enemy can scavenge and reuse them, the way Charlie did much too well w/ discarded US ordnance in Nam.

Why a training version? Because men must practice w/ these weapons a lot”

The disposable grenade launcher offers several advantages over both rifle grenades and grenade cartridges but I was uncertain that it could be adapted to hand throwing. Large components such as parts of the trigger mechanism seemed likely to carry far enough to endanger the thrower. The obvious answer is to design the device so that the trigger unit needs to be detached to arm the weapon for hand throwing. This would just leave the grenade, the launching spigot and the outer case: something about the size of a tin can/offensive grenade.

UPDATE

Small grenades of similar power to the current 40mm would be very useful for “reconnaissance by fire” tasks: in other words shooting the bushes to see what jumps out. Many tanks in Vietnam carried an M79 for this purpose and used either explosive or CS rounds. Small-calibre DGLs mounted on a Tanker MP would be an easier weapon to handle from a vehicle hatch.

For anti-vehicle tasks an alternative to HEAT rounds might be an EFP (Explosively Formed Penetrator) grenade. This technology has begun to be offered for RPG-7 rounds. The rocket warhead detonates about 30m after launch and creates a slug of metal moving at around 2,800m/s. Due to its short time of flight the projectile has a very high hit probability and is not effected by countermeasures such as RPG cages/slat armour. EFP offers the infantryman considerable capability against helicopters. This technology has been used for some artillery delivered sub-munitions but to the best of my knowledge hasn’t been tried with rifle grenades. One Russian EFP round for the RPG-7 has a detachable segmented “splitter ring” assembly. If the round is fired with this in place the slug of metal is shattered into a shower of fragments for anti-personnel use. In effect this converts the round into a “Flying Claymore”.

DGL systems could also be used to fire large-calibre anti-armour grenades.

One of the main problems with grenade systems such as the 40x46mm M203 is that the relatively small effect area of the grenade requires it to be placed close to the target. Since the round has a low velocity and curved trajectory this can be difficult.

The prototype Ring Airfoil Grenades have demonstrated that it is possible to fire higher velocity grenades long distances at a fairly flat trajectories and low elevations. Fuse technology has advanced considerably since the 1970s so it may be prudent to take another look at the potential of explosive RAGs as an infantry weapon. The DGL concept would be a very useful way to introduce this capability.

By the Author of the Scrapboard : Blog of the Books.
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