SOME WW1 BRITISH GRENADES

Before the war start, two Belgian citizens - Albert Dewandre (an engineer) and the Captain Léon Roland (from the Compagnie Belge des Munitions Militaires) - designed the principles of this modern grenade : an automatic ignition system fully located inside the grenade body and therefore waterproofed. The start of the great war brutally stopped this invention development (the Captain Roland being capured by the Germans as a prisonner). But a talented English manufacturer, William Mills, who met Dewandre at the end of 1914, made the theoretical concept possible, and introduced a patent as soon as February 1915.

The grenade n°5 MkI (Mills patent) finally appeared on the front in May 1915, but its distribution to the fighting units was relatively slow : some British soldiers were not given such weapons before another year. This grenade was made of a outside prefragmented cast iron body, with a lateral filling hole, another hole at its top for plugging the striker lever mechanism, and a bigger hole at the bottom shut by a brass base plug giving access to the igniter body.

The ignition system was contained into a central compact body : a mobile firing striker compressed with a spring was facing a starter cap fixed behind the grenade bottom plug. The firing striker top was attached to an external striker lever secured by a safety pin. To use the grenade, a soldier just had to remove the safety pin and keep the striker lever pressed with the grenade body inside his palm. When the projectile was launched, the freed spring action moved the lever up, propulsed the firing striker pin towards the starter cap, whose ignition set fire to a delayed wick, finally igniting the detonator after time delayed combustion.

Safe and waterproof, this grenade has been by far the best handgrenade of WW1, and was even adapted as a rod rifle grenade by the addition of specific devices. The Mills system has been the subject of 3 major evolutions during the war :

• N°5 MkI and MkII hand grenade : the MkII lever was made more rigid thanks to a bend
• N°23 MkI, MkII and MkIII hand and rifle grenade : the MkI appeared in 1917 with a narrower base and a base plug drilled with a central threaded hole for the optional screwing of the rod needed to transform the projectile into a rifle grenade. The MkII and MkIII were variants only designed to improve the manufacturing productivity and lower the production costs.
• N°36 MkI hand grenade : May 1918 evolution, rounder 'belly' for a more stable station in the rifle launching device, and larger safety pin location ears.

These differnt version life was so long that this grenade was still in use in WW2, and only removed from the active service in the 70s ! More than 50 millions Mills grenades have been produced during WW1, all variants included, by more than a hundred subcontractors. Its handsome shape, fragmentation properties and internal igniting device both safe and waterproof were the fundamentals of this huge success.

Weight 770 g, including the diverse expolosies used (Alumatol + Abelite + Cilferite, or Amatol, or Ammonal + Bellite)

The small and handy German egg grenade '('Eierhandgranate')' inspired the British designers who introduced in the end of 1917 a copy made of a cast iron body and a simple percussion igniting plug, with a 5 seconds delay. This new Hand Grenade n°34 is known in 4 successive variants :

• hand grenade N°34 MkI, ovoidal body shape with a percussion igniter, safety spring and removable safety pin, delay 5 seconds
• hand grenade N°34 MkII, shape identical to the one of the MkI with a percussion igniting plug, shearable metallic safety wire and safety pin, delay 7 seconds
• hand grenade N°34 MkIII, elongated ovoidal shape with the MkII percussion pin
• hand grenade N°34 MkIV, shorten ovoidal shape and prefragmented belt, with the MkII percussion pin

All 4 models were equipped with a brass plug closing a lateral filling hole.

Unknown weight, alumatol explosive

Capitalizing the experience acquired with the manufacturing and use of the rifle grenade N°2, the company Marten Hale Cotton Powder Ltd designed a new percussion rifle grenade equipped with a much more sophisticated safety system, and a bigger lethal power.

This 'Commercial' Marten Hale percussion grenade body was now a steel cylinder, externally prefragmented, with a small tube inserted axially and carrying a detonator and a starter cap. A mobile needle pellet secured from the starter by a safety 'creep spring' was located inside a brass base piece. The mobile needle pellet movements were made impossible at rest by two lateral retaining bolts blocked under a wind vane rotating ring. A sliding releasing socket equipped with a safety pin was impeding the vertical movements of this wind vane ring.

Before use, the safety pin had first to be removed. At the departure, the momentum pulled the releasing socket back. The flight air flow rotated the impeller of the wind vane around a thread, finally freeing the lateral movements of the retaining bolts. Then only the needle pellet movements were made possible after 10 meters of flight, for a percussion detonation at the impact.

This grenade could be used as a hand grenade (with a wooden handle and a string), or as a rifle grenade (with a 10 inches rod and spring clips for securing the grenade on the rifle tube). It was never officially adopted by the Britsh Army, but imortant stocks of 'Commercial' Marten Hale grenades were used by the British soldiers in 1915.

Meanwhile the British Army ordered Marten Hale the design of a very similar model, only differenciated by a thin brass base piece instead of an aluminium thick one. This grenade became officially the rifle grenade N°3 MkI in February 1915.

The rifle grenade N°3 MkII only differed from the MkI by a little alteration of the external shape to improve the aerodynamics properties and the air flow on the wind vane (elongation of the body length, and smoother transition between the cylinder base and the brass base piece)

Unknown weight, ammonal, amatol or TNT explosive

As seen above on this page, the new rifle grenade N°3 inspired from the commercial percussion grenade Marten Hale appears in 1915. This design solved most of the safety issues associated to the rifle grenade N°2. However, if the ingenious mechanism based on the release of the safety chain by the in-flight air flow on a wind vane was efficient, it also induced too much manufacturing complexity and costs.

The rifle grenade n°20 Mk I, dated June 1917, is a simplification of the rifle grenade n°3, making it more economic and simple to manufacture, without sacrifying anything on the safety side. Both the externally prefragmented steel body and the internal percussion detonator mechanism remain unchanged, but the safety wind vane is replaced by a simple sliding releasing socket pulled back by the departure momentum, blocked at rest by a safety pin.

A further simplification of the steel body machining was introduced later with the rifle grenade n°20 Mk II, whose prefragmented body was only having parallel circular machined grooves instead of the classical square pattern.

As all these kinds of projectiles, this rifle grenade was used inserting the tail rod inside a usual infantry rifle gun, but armed with a blank cartridge bullet-free. The accidental use of a conventionnal bullet was the main cause of incidents.

One should note in the same family the

• rifle grenade N°20 conversion Mk I : N°3 MkI grenade body mounted on the N°20 new base
• rifle grenade N°20 conversion Mk II : N°3 MkII grenade body mounted on the N°20 new base

Weight unknown, ammonal

From May 1915, the British Army organizes in Hazebrouck the manufacturing of prefragmented hand grenades having the shape of a grapefruit grain (in French 'Pépin') named 'Hand grenade Newton Pépin'. Dangerous, they will inspire the French grenade Citron Foug, as well as the British rifle grenade N°17 MkI (June 1917), that has been rapidly improved to become the rifle grenade N°22 Mk I.

Just as the original handgrenade model, this grenade was composed of an externally prefragmented steel body and a central detonator. On the top of the body, a percussion pin bearing soft metal cap was covering the grenade and was equipped with a safety pin. This apparatus was made to provoke an explosion at the impact. Attached to a 38cm rifle rod, this grenade was exploding too often on the departure shock action.

This problem was partly fixed with a October 1917 evolution, the rifle grenade N°22 Mk II whose percussion pin bearer cap was lighter and less enclined to be affected by the departure momentum. It was not equipped with a safety pin anymore.

Unknown weight, ammonal, amatol or alumatol

The rifle grenade N°24 Mk I is another June 1917 simplification of the rifle grenades series N°3 and N°20.

Changes are only applied to the parts shapes and dimensions, but the way it worked was strictly similar to the preceeding models, so that no specific training was needed for its use. The prefragmented body was machined with external circular parallel grooves only.

A further simplifacation was adopted suppressing every external fragmentation grooves with the rifle grenade N°24 Mk II dated May 1918, whose cast iron body was smooth, all the other components being unchanged.

Unknown weight, ammonal, amatol or alumatol

Ultimate evolution dated May 1918 of the prolific British rifle grenades family, the rifle grenade N°35 Mk I is a simplification of the rifle grenade Nr24 MkII, whose brass body has been shortened further and whose safety pin is passing through the sliding socket instead of below it.

In an exhaustive spirit, one must note the rifle grenade N°35 Mk II with an improved water-proof property for use on the Middle-East front.

Poids inconnu, ammonal, amatol ou alumatol