One of my favourite war films is the Dogs of War, an adaptation of the Frederick Forysthe novel of the same name. A most memorable scenes is the final assault, in which a monstrosity of a multi-shot grenade launcher is deployed to great effect.
It was called the XM-18E1R in the film but was actually called a the Manville Gun, in 25mm , a weapon with a fascinating history.
Charles Manville developed the original version in the mid 1930’s for use in public order control, built in 12 Gauge, 26.5mm and 37mm. Although it did not win any production contracts for WWII the three calibre variants were developed to include a number of ammunition types, flares and tear gas for example. After only limited sales because of its weight, production ceased in 1943.
A couple of videos…
After the film, Hawk Engineering in the USA produced a near copy called the Hawk MM1.
The Anti Riot Weapon ENfield (ARWEN), from the late seventies, is perhaps a similar weapon, certainly for the non lethal ammunition. Now owned and produced by Police Ordnance in the USA.