The JM cloche is an element of the Maginot Line

Maginot Line

The Maginot Line , named after the French Minister of War André Maginot, was a line of concrete fortifications, tank obstacles, artillery casemates, machine gun posts, and other defences, which France constructed along its borders with Germany and Italy, in light of its experience in World War I,...

. It is a non-retractable non-rotating cupola of steel alloy like GFM cloche

GFM cloche

The GFM cloche was one of the most common defensive armaments on the Maginot Line. A cloche was a fixed and non-retractable firing position made of a thick iron casting which shielded its occupant...

s, but are armed with twin heavy machine gun

Machine gun

A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....

s, as opposed to the lighter automatic rifle

Automatic rifle

Automatic rifle is a term generally used to describe a semi-automatic rifle chambered for a rifle cartridge, capable of delivering both semi- and full automatic fire...

s associated with the GFM. There are 179 JM cloches on the Maginot Line

Maginot Line

The Maginot Line , named after the French Minister of War André Maginot, was a line of concrete fortifications, tank obstacles, artillery casemates, machine gun posts, and other defences, which France constructed along its borders with Germany and Italy, in light of its experience in World War I,...

.

JM is an acronym for Jumelage de Mitrailleuses (twin machine guns). While the MAC 31 heavy machine guns were of the same caliber (7.5mm) as the GFM guns, they had a longer practical range 1200 metres (3,937 ft) and a maximum range of 4900 metres (16,076.1 ft), with a 500 round per minute rate of fire.

Description

The JM cloche closely resembles the GFM cloche in size and construction. It exists in three versions, all designed Model 1930: small, large and two-man. JM cloches had a single firing port, which was flanked on either side by trapezoidal observation ports. The blank rear was frequently backed by a concrete-covered embankment, which provided additional cover and reduced the prominence of the cloche.

AM cloche

The AM (Armes Mixte) cloche, Model 1934, could mount a 25mm anti-tank gun and paired machine guns in two separate ports. It lacked the JM's observation ports. Shutters could be put in place to close unused ports. The AM existed in both a large and a small version. 72 AM cloches were installed solely in the New Fronts fortifications.

AM conversions

Ten JM cloches were modified to accept a shortened 25mm anti-tank gun in place of the twin machine guns. The modifications took place in 1940 in several ouvrages of the northeast.