US Army WW1 rifle grenade launcher for V-B grenade

Upon entering World War I, the United States attempted to adopt the V-B grenade, but this was not very successful. The difference between the French and American service cartridges (8 mm vs. 7.62 mm) meant that the grenade had to be re-designed with a smaller hole, but even this was not sufficient to ensure reliable functioning, due to differences in bullet design. The American bullet would often break apart in the grenade, and this led to the V-B derived grenade design being scrapped in May 1918