In 1907, Frederick Marten Hale (sometimes Martin) developed the rod grenade.
[5][6] "A simple rod was attached to a specialized grenade, inserted into the barrel of a standard service rifle and launched using a blank cartridge.
"[6] However, the British did not immediately adopt the idea and entered World War I without any rifle grenades.
[4] As soon as trench warfare started, however, there was a sudden need for rifle grenades.
[7] The Hales grenade was improved throughout World War I to make it more reliable and easier to manufacture.
This led to the search for an alternative and resulted in the reappearance of the cup launcher during the latter years of World War I.
It has an externally segmented body and a wind vane designed to help activate the detonator in mid flight.
Practically, the vane was a significant problem; it was hard to align properly and adverse weather, such as rain, strong winds or even a particle of dust could prevent the vane from operating correctly, which caused a failure.
3 also had an overly sensitive percussion cap, which caused many premature detonations.
20 used ammonite, which tended to corrode the brass parts of the grenade, which created several failures when it was fired.
3, while the Mk II used a weldless steel tube and had circumferential grooves for fragmentation.
20 with a less sensitive percussion cap and refined ammonite that did not corrode the brass parts of the grenade.
24 MK II that had a detonator holder that used a small arms cartridge and a shorter striker.