This is the M13 Gewehrgranate, a high-explosive cast-iron rifle grenade fitted with a percussion fuse designed to explode on impact, its body segmented for maximum fragmentation on detonation.
It was the British who invented the rifle grenade, the first design of which was patented by Frederick Marten Hale in November 1909, but it was the Germans who were the only one of the belligerent countries that entered the Great War with not only a bespoke hand grenade at their disposal, but also a rifle grenade. That’s forward-thinking for you, or lack of, depending on whose side you’re on. This posed photograph shows two German soldiers about to fire an M13, three more of which are stacked up in the foreground. The man on the left holds a string with which to pull the trigger of a Mauser rifle attached to a metal frame, stabilised with sandbags, to not only improve accuracy, but to make firing the grenade both safer and easier.
The metal frame is actually one of these, the Schießgestell (shooting frame) Model 1915,…
…although before that there was the Schießgestell Model 1913, designed specifically for the Mauser-fired M13 rifle grenade, and seen in diagram on the left, and in the illustration on the right with rifle attached, and M13 grenade ready to fire. The M13 grenade would be superseded by the M14, and because the Great War occurred between 1914 & 1918 and not 1913 & 1918, photographs of the M13 ‘in action’ are few and far between; the earlier photograph is the only one I happen to have, and my photo-library is vast, so if anyone has any M13 pictures to spare……?
This is the business end of the M13 grenade,…
…here with what was referred to as a ranging disc attached,…
…as seen at the top of this diagram. The ranging disc was fitted when required to limit the range of the grenade, which could, without disc, reach a target close to four hundred yards distant, and was not, as you might read elsewhere, some device to prevent the grenade from penetrating too deep on impact before exploding; basic aerodynamics, your honour, versus basic metal density. Which is not to say that aerodynamics weren’t a problem too, because the very aerodynamicity of this grenade did mean that it was prone to sink too deep into soft ground before exploding, negating the fragmentary effect of the blast, but this disc wasn’t the solution. Vorstecker vor Abschussherausziehen is a reminder to remove the plug (safety pin) before firing.
So, here’s the basic body of the grenade,…
…and here, on the left, is the view from the top. The brass sleeve down the centre of the grenade allowed the detonator holder sleeve, containing a percussion cap & detonator, and topped with an igniter plug, to be screwed into the head of the grenade through the hole seen here on the left, rather like the officer in the picture on the right is about to do, although he is not holding an M13, and I am not going to explain any more, as we shall see this picture again (although not this post).
Close-ups of the igniter plug, in place (left), and removed from the grenade (right), showing the remains of the detonator after it has done its deadly work,…
…the whole igniter (fuse) marked in mauve on the diagram above. Already inside the grenade, a creep spring (for creep, read weak) sits above the main striker, marked in red, and the striker pellet, highlighted in orange, but the majority of the working parts are to be found in the brass base cup (right),…
…seen here screwed into the base of the grenade.
Cup (left) & cup diagram (right), both to the same scale. At the top of the diagram, above the cup, is the end of the brass sleeve with the bottom of the striker pellet, still highlighted in orange, inside. The concussion system within the cup would be set off on firing, at which point the whole internal assembly moves slightly forward, the percussion cap igniting the black powder pellet (marked in blue) which served, up to this point, as a safety device. Once the powder had gone, the striker pellet (in orange, remember) & striker needle at its far end (in red on the previous diagram) could now move, and, on impact, push forward through the creep string, strike the percussion cap, set off the detonator, and explode the grenade. The gas escape vents marked on the above diagram, and visible in both the photo on the left and the previous photo, allowed oxygen to enter pre-combustion, and gas to escape post-combustion.
This diagram was first published in 1917 and is also supposed to be an M13, although the British illustrator appears to have had little idea of the real shape of the grenade. You can decide for yourselves how well he did with the internal workings of the base cup compared to the same-scale cut-out on the right.
An eighteen-inch copper-coated steel rod screwed into the other end of the base cup completes the assembly.
And if that all seems rather complicated, well, I suppose it was, the fact that this grenade would soon be replaced by the M14, which is what the German officer is actually holding in the earlier photo, suggesting that what appeared to work on the drawing board might not have been quite so successful in the field.