Grenade Launchers: The Spigots

“Rifle grenades are regarded as the rifleman’s most reliable weapon against tanks, pill boxes, and exposed enemy personnel. At first, they may seem to be too small to do much damage, but their power is far greater than appearances would lead us to believe.”
Guidebook for Marines, Chapter 20, p.257 1951
Spigot-launched rifle grenades are a little bit better known than cup and rod grenades. Very occasionally, they appear in movies. The best examples I can think of are in “Battle of the Bulge” and “From Russia With Love”.
The principle of a spigot launcher is very simple. Rather than fitting down a barrel, the projectile has a tube that fits over the outside of the barrel. I have not encountered any examples of spigot launchers being used on rifles in the First World War. The principle was known at this time, since the Granatenwerfer 16 was an example of a spigot mortar.
When spigot grenades were introduced, the rifles they were intended to be used with were not entirely suitable. Launching required an unobstructed length of barrel and a service rifle has structures such as bayonet lugs, foresights and woodwork in the way. The spigot launcher was therefore a length of tube that extended the barrel.
A number of spigot launchers for rifle grenades were in use in the Second World War.
The German example represents a very simple model of spigot launcher. It attaches using the bayonet lug and has a foresight for aiming grenades. The only projectile used was a 60mm hollow-charge anti-tank grenade.
The Japanese also made use of a spigot launcher. This was 15cm long and had a 27mm external diameter. It could be mounted on Type 38 6.5mm rifles.
Two types of projectile were used with the Japanese Army spigot launcher.
The fragmentation bomb was a Type 91 hand grenade with a tail unit screwed on. Range was around 110 yards with the grenade exploding once the 7-9 second fuse burned down. Time of flight was four seconds, so detonation was generally after the grenade had impacted.
The smoke-screening bomb was a dedicated rifle grenade weighing 1.3 lb and using HC composition. Range was approximately 150 yards.
The poor performance of the army ’s spigot launcher lead to developement of the Type 100 cup discharger.
Around 1942 the Japanese Navy developed its own spigot launcher using a hollow-charge grenade with a 55 yd effective range and 40mm of penetration.
Also used with this launcher were the Type 2 and Type 3 Model 1 rifle grenades. Both of these were mpact-fused fragmentation grenades based on the Type 99 grenade. Maximum range for these grenades was about 224 yards.
Grenades for the spigot launcher were projected by a cartridge mounting a wooden bullet.
The British produced a spigot launcher for the No.4 rifle. Like many designs it had a flip up ladder sight. This was marked in increments of 25 yd from 25 to 100. The No.85 51mm anti-tank grenade (1.26lb) externally resembles the M9A1. The No.87 was a WP rifle grenade (1.25 lb). Post war, this launcher could also use the No.94 Energa anti-tank grenade. One man per platoon was issued the Energa as a replacement for the PIAT.

The US had four models of 22mm spigot launcher in use during World War Two. The M1 was for the M1903, the M2 for the M1917, the M7 for the M1 Garand and the M8 for the M1/M2 carbine. The M76 was introduced with the M14 in the 1950s.
The M7 was not issued until late 1943 and issue of the M8 had been held back until the M7 was also ready. Prior to this, American forces only used grenade launchers on M1903 bolt-action rifles, one such rifle being issued to the platoon for grenade-launching.
The Korean War-era Infantry Field Manual FM 7-10 (Ch.1, p.2) still states that a rifle squad is provided with one M1903 bolt-action Springfield for launching rifle-grenades. This may just be a failure to update the manual. The actual situation in practice may have been different.
By 1943, the M7 was in service, ten being provided to a rifle platoon. One was used by the platoon-guide and one by each squad corporal. Two more were issued to individual riflemen in the squad. The M8 was used by a carbine-armed troops, and typically found issued to messengers, drivers, ammo-bearers and the company bugler. The bugler and messengers often served as drivers for jeeps or ¾-ton trucks.
The exterior of American grenade launchers have grooves or rings. These are graduations used in setting the range of a grenade. By varying how far down the tube the grenade is positioned, pressure and launch velocity can be varied.
When the launcher was used for high-angle fire some means of keeping the grenade at the desired graduation was needed.
For the M1 (M1903) and M2 (M1917) launchers a separate launcher position clip was attached at the desired level. Several of these clips were packed with certain rifle grenade types (WP and Frag).
Grenade Launcher Position Clips
Launcher Position Clips for the M1 and M2 Grenade Launcher.
The M7 and M8 had a spring fitted near the launcher’s muzzle. This provided sufficient friction to keep the grenade in place until fired. Apparently these springs were very prone to breaking until the A2 modifications after the war.
If a grenade was fired from the semi-automatic Garand, the bolt would unlock before the grenade was fully under way. This caused a drop in pressure and reduced grenade performance. The M7 included a mechanism to shut off the Garand’s gas system, keeping the breech closed. When fitted with a grenade launcher it was necessary to hand cycle the bolt after each shot.
By the Korean war the M7A2/A3 launchers were in service. These had a modification so they only shut off the gas system when a grenade was being fired. It was no longer necessary to remove the launcher to have the rifle function semi-automatically. The M1/M2 carbine had a different mechanism and functioned semi-automatically with or without grenades.
Many armies teach soldiers to hold rifles with the butt underarm when firing grenades at low trajectories. The US Army manuals do not mention this and taught that grenade launchers could be fired from the shoulder. Helpfully, it does suggest the butt be well seated against the shoulder, the thumb held on the outside of the grip and the head well back from the sight. A body position where the body can move with the recoil was required. If prone, the shoulder should not be used. Instead some means such as a rut in the earth be used. When firing from a foxhole the back wall of the trench could be used.

For high-angle fire, the weapon was fired with the butt against the ground. A rubber recoil pad was available for the Garand. The carbine was held on its side so that both the heel and toe of the butt were in contact with the ground. The rifle or carbine was held at 30, 45 or 60 degrees and range adjusted by how far the grenade was slid down the spigot.
Maximum range was increased by use of the “M7 Auxiliary Cartridge” (aka “Vitamin Pill”). This was a booster charge in what resembled (and may have been) a .45 Long Colt casing. The cartridge was inserted in the muzzle of the launcher before a grenade was fitted. The “Guidebook for Marines, 1951” cautions the auxiliary cartridge should not be used when shoulder- firing due to “a tremendous wallop”.
Use of the vitamin pill in the carbine was only for emergencies, since the stock was not considered strong enough. Use of the vitamin pill was discontinued around 1954.
The different grenades had different ballistic behaviours, so for each there was a table showing which angle and “ring position” was required for a given range. 
A rotatable grenade sight (M15) with a spirit level could be fitted to the side of the stock. Interestingly, later field manuals for the M79 detail how M15 sights can be fitted to that weapon.

All grenades were fired by blank cartridges. This could be fiddly for the Garand. A cartridge was loaded directly into the breech (risking “Garand thumb” ) or the weapon unloaded and reloaded with a clip of blanks. Using a clip-loading mechanism, the Garand magazine could not simply be topped up with loose blanks.
Blank cartridges for grenade projection are sometimes called “Ballistite” after the powder composition used in some examples. The term “ballistic” may also be encountered.
High trajectory ranges for M8 launcher on M1 Carbine

Ammunition for the American grenade launchers included:
M9/M9A1 (1.23 lb) 48mm hollow-charge anti-tank grenade. In a later war North Vietnamese forces used these fired from M44 Mosin-Nagan carbines.
M17 anti-personnel grenade. (1.47 lb) Mk2 “pineapple” grenade body with M9 rifle grenade tail. Impact fused.
M19 Smoke WP (1.5 lb). Screening, marking, anti-personnel and incendiary.
M20 Smoke HC. Screening smoke.
M22 Smoke Signalling. (1.26 lb) Emit coloured smoke for a minute after impact. Green, red, violet or yellow.
M23 Smoke streamer (1.16 lb). Before firing a section of tape on the nose must be removed to expose an air intake. Ten yards after launch produces a stream of smoke along its trajectory and for at least 12 seconds after firing. Green, red, violet or yellow. Maximum altitude Rifle: 155 yd in 11 sec, 203 yd in 12.4 sec with booster. Carbine: 97 yd in 8.5 sec, 133 yd in 10 sec with booster.
Parachute Flare. White, red, amber or green.
Five-star flare. White, red, amber or green.
M1-series Projection Adaptor. Tail unit for the Mk.2 hand grenade. A clip on one of the claws held the safety lever in position when the pin was removed. Firing causes the clip to setback and release the lever. Could also be used with the M34 WP grenade. Later model could be used with the M26 hand grenade. 0.38 lb plus grenade weight. WW2 60mm mortar warheads could also be thrown with this projector, for half the usual range. Later models of fuse will probably not arm if used this way.
M2-series Projection Adaptor. Tail unit for cylindrical, flat-bottomed grenades such as smoke, thermite, tear gas or the Mk3 offensive grenade.

During the Korean War it became apparent that something more potent than the M9A1 was needed. The US Army adopted the 75mm Energa grenade as the M28. A longer version of the M7, the M7A3, was introduced. The M28 was replaced by the M31, a 1.56 lb 66mm grenade of American origin. Performance of the two models is effectively the same, both giving around 200mm of penetration. 
High Trajectory Ranges:
M9A1 anti-tank. Rifle: 255 yd, or 365 with booster. Carbine: 185 yd, or 235 with booster. In theory it was possible for a high-angle shot to hit the thinner upper armour of a tank. In practice, the low velocity and wind effects made this difficult.
M17 anti-personnel. Rifle: 200 yd, 290 with booster. Carbine: 135 yd.
Mk2 Frag in M1 adapter: Rifle: 180 yd, or 225 with booster. Carbine: 130 yd.
Chemical grenade in M2 adapter: Rifle: 146 yd, or 192 yd with booster. Carbine: 95 yd, 124 yd with booster.
M19/M20 Smoke grenades: Rifle: 215 yd, or 310 with booster. Carbine: 150 yd, or 215 with booster.
Flat Trajectory Ranges (up to 10 degrees elevation):
M9A1 anti-tank. Rifle: 104 yd, or 175 yd with booster at 10 degrees. 215/315 at 25 degrees. Carbine: 70 yd at 10 degrees, 149 yd at 25 degrees.
Time of flight about 25 yd in ½ second, 50 yd in 1¼ second. Lead for a target at 15 mph at 50 yd is 8 yd.
Mk.2 hand grenade in M1 adapter. Rifle: 50 yd in one second, 80 yd in 1.7 sec. Carbine: 39 yd in one second, 48 yd in 1.3 sec.
M17 Impact-Frag. Rifle: 74 yds, Carbine: 51 yd.
While American soldiers were provided with grenade launchers and a wide range of ammunition types, it was noted in Infantry School Quarterly Vol.45-46, April 1956 p.82. “Rifle: grenades have long been a neglected and misused weapon, primarily because of misinterpretation and lack of information on their use. They are, however, the only antitank weapons of the rifle company other than the 3.5-inch rocket launchers. Not only are rifle grenades the antitank weapon of the rifle squad, they are also the squad’s “mortar” for indirect firing at area targets.”
A report on weapons use in the Korean War found no accounts of rifle grenades being used by US troops, although it did note there were incidences when they would have been useful. In all the units interviewed, troops had thrown their grenade launchers away. The same report notes that the CCF (Communist Chinese Forces) did use grenade launchers. One wonders how many of these were items discarded by American troops!
While ingenious, the “ring and angle” range system does seem rather involved for a squad-level weapon that was intended to be used in close proximity to the enemy. In the trenches of Korea, grenade launchers may have been more effective if grouped into sections at platoon-level. Notable is that may other models of spigot launcher have rings or graduations, but do not appear to have a means of holding the grenade in a set position. This would not be the only instance of a piece of design being copied without understanding of function.
By the Vietnam-era the heavy M31 grenade was out of favour. It was not likely to perform adequately with the weaker 5.56mm ammunition and recoil would be even worse with the lighter M16. The M72 LAW and M79 seemed more promising. As is often its wont, disillusionment with one weapon caused the US Army to ignore the entire field. Potentially useful other types of rifle grenade were not made available to soldiers. For example, no adequate smoke screening round for the M79/M203 has ever been issued.


In May 1933, the provincial government of Yunnan purchased 200 Brandt launcher attachments and 10,000 Mle.31 spigot grenades.
The Mle.31 was an early example of a bullet-trap grenade. A grenade massed 450 grams (1 lb) and the launcher attachment 300 grams (0.66 lb). Range was 325 metres (355 yards).
Brandt Mle.31 rifle grenade,
Chinese forces in Burma were mainly equipped with American weapons. One rifle per rifle section was an M1903 mounting an M1 launcher. This was primarily intended for use with the M9 anti-tank grenade, although other types were available.
Most of the rifle section would be armed with M1917, which were often shortened in Chinese units to make them handier.
Either the M2 launcher was not available in adequate numbers or the shortened M1917 rifles were no longer compatible with mounting the M1.
Shipments of American grenade launchers and their grenades did not begin to appear in significant numbers in mainland China until spring 1945.
Chinese forces in the Korean War made good use of grenade-launchers mounted on M1903s.
In contrast, American troops in Korea often discarded their issued grenade-launchers and other gear. Doubtless, many of these discarded weapons reached Chinese and North Korean forces and saw use.
Post-war China has manufactured a variety of spigot rifle-grenades, including copies of the Energa.
Some armies have remained enthusiastic users of rifle grenades. These include the Israelis, French, South Africans and Rhodesians. Belgium, Italy and China manufacture a range of models.
The Rhodesians often issued Energa grenades to the point man of a patrol, giving him RPG-level firepower during an encounter without the problems of back-blast and the added weight of a launcher. In a four-man Fire-force “stick” the two riflemen might each carry one or two rifle grenades.
The Rhodesians issued two cartridges for grenade projection. The full-power load (440 yd) was for high-angle fire with the butt against the ground. The reduced charge was for short-range (165 yd) “underarm” firing. It was considered a good joke to trick a comrade into firing the full-power load underarm or from the shoulder. It was prudent to keep your fingers out of the trigger guard and your thumb away from the pistol grip when firing grenades. The recoil could break them.
Using rifle grenades in semi-automatic rifles had introduced new complications. Propellant gases could escape from the opening breech or via the gas regulator. For many designs it was necessary to close the gas port to the barrel so the bolt could not cycle. The weapon needed to be manually cocked between each shot. On some designs the grenade sights are connected to the gas port. Flipping up the sight automatically closes the gas supply. Often a grenade cannot be placed fully over the muzzle if the grenade sights are not raised. Reloading the weapon with blank rounds was often slower with semi-automatics. Most self-loaders are not designed so that a magazine can be topped up with loose rounds while in position. The magazine needed to be removed, the chamber cleared and a new magazine of blanks inserted and a blank round chambered.

AP/AV700 Multiple Grenade Launcher

The Italian Franchi AP/AV700 was a prototype weapon (c.1985) that used an unusual way to utilize spigot grenades.
Italian Multiple Grenade Launcher
Attached to the baseplate were three barrels. These barrels were chambered either for 7.62mm NATO ball rounds or for 5.56x45mm ball. The bore of the barrel was conical, so was loaded by simply dropping the correct-sized round down the muzzle.
The bullet-trap rifle-grenades designed for this launcher were rocket-assisted and had a range of 765 yards. Each massed 2.06lbs. The 1lb warhead was described as HEAT-MP-Frag: a shaped-charge with additional anti-personnel and blast effects. Penetration was 120mm (4.72") The grenades could also be fired conventionally from a rifle muzzle. The launcher could probably be used with other models of rifle-grenade with a 22mm calibre tail.
The launcher alone massed 24.25lbs and could be carried by one man on a special backpack. Grenades could be fired singly or as a salvo of two or three. Up to six or seven salvoes per minute were possible. Accuracy was claimed to be superior to launching a grenade from a rifle.
As well as providing additional firepower for fixed positions or ambushes, the weapon could potentially have been mounted on vehicles or boats.
Around 1994, the design had evolved into the two-barrelled GLF-90. The launcher massed 17.6lb. The GLF-90 in 5.56mm could launch a 1.1lb grenade 569 yards and a 0.88lb 656 yards. The 7.62mm version launches a 1.1lb grenade to 689 yards and an 0.88lb grenade to 984 yards. Minimum range for all is 100 yards.
Neither the AP/AV700 nor the GLF-90 entered production.
The original reason for the spigot launcher was that rifle barrels had not been designed with grenade-launching in mind. This was to eventually change, and by the late 70s the latest designs of rifle had foresights not mounted at the muzzle and 22mm flash-hinders that also served as grenade spigots. Although assumed to be a “NATO standard”, the common 22mm dimension was arrived at without official intervention. The various manufacturers emulated each other and were influenced by the rifle-grenades already in service.
The separate spigot launcher remained in use for some weapons. When creating the M14 from the Garand, the separate M76 launcher was developed rather than designing the flash-hinder as an integral launcher. Some FAL rifles had integral launchers, while others (such as the British L1A1 SLR) required an attachment. The position of the SKS and AKM’s foresight required an add-on launcher for those nations that used rifle-grenades with these weapons. Below is a Polish example of an AK. External diameter of the launcher is 20mm. Many Yugoslavian SKS have grenade launchers. The Hungarian AMP-69 does not have a detachable spigot. Instead, the whole rifle has been reconfigured for grenade launching. A buffered stock and sliding fore-end help mitigate the effects of recoil. The gas tube is fitted with a cut-out.

As integral launchers became commonplace on military rifles spigot attachments became obsolete. Rifle grenades had not finished evolving, however. That is a story for another post.