Based on the Martini–Henry service rifle the Greener shotgun is a breech-loading, single-shot lever-actuated falling block,a design that first entered service with the British Empire in 1871.
The Greener Police Gun came into existence shortly after WW1 , it was chambered in a special round designed and produced exclusively for it. The 12-14ga shells made the shotgun useless to anyone who stole it, because the shell stepped down from 12ga to 14ga in the middle of the chamber standard 12ga shotgun shells wouldn’t chamber. They also incorporated a trident style firing pin matched by a rebate in the head of the case, attempting to fire standard shells if you did manage to squeeze them in wouldn’t work because the two outer pins prevented the firing from striking the primer.
The Police Shotguns were used mostly by prison guards and colonial troops for riot control, but were also produced commercially in limited numbers. Despite the design being well and truly an antique it can still be found in the hands of troops in some developing country today as seen here in Burma.
The success of the Police Gun led Greener to develop the Greener GP single-barreled shotgun firing standard 12-bore ammunition, which was a staple for British gamekeepers and economy minded shooters. It was produced up until the 1960s and is still used today by many hunters including myself.
I finally got myself a Mk3 Greener police.
Mine was made in 1958 (to the best of my knowledge) and was issued to the Hong Kong police, the serial No. Is in the 12k range and other than a tiny bit of surface rust on the nose cap it’s pretty much mint. @no1mk3 do you have, or know someone with a cart case for it that I could get some measurements off?
It seems the MK3 and its ammo was in response to modified 16 g shells being able to work in the earlier patterns.
"Another request was that the gun should use proprietary ammunition, not available through commercial channels. This was requested to made illegal use of guns, stolen or taken away from police more complicated for criminals. This request was fullfilled by famous British gunmaker W.W. Greener, who developed a single-shot shotgun, based on the long-obsolete but rugged Martiny single-shot action. This new gun fired proprietary 14 gauge shells, loaded with shot, and featured very rugged wooden full stock with steel nose cap and buttplate, so it can be safely and routinely used not only as a gun, but also as a club, banging doors and occasional hot heads in the course of upkeeping the law and order.
Greener police gun mark I appeared in around 1921, and tens of thousands were delivered to organisations like Egyptean colonial police etc. However, it was soon discovered that criminals, who managed to get hold on Greener guns, used standard 16 gauge shells, tightly wrapped into paper or tape to fire from Greener guns. To made commercial ammunition completely unusable, Greener responded with improved design, Greener police gun mark III. This gun used proprietary ammunition with bottlenecked case made of brass, with thick rim. Base of the case was roughly same as standard 12 gauge case, but toward the forward end of the shell it has reduced diameter equivalent to 14 gauge shell size. To further complicate illegal use of its police shotgun, Greener provided its Mark III guns with trident-shaped strikers. Greener police shells had grooved base and recessed primers, and attempt to fire any commercially available shell from Greener gun would fail every time as the side projections of the striker would hit the flat base of the shell, stopping the central part (the firing pin itself) before it can reach the primer."