ZB vehicles could be considered as belonging to an AMR 35 variant. Heavier armament As the 7.5 mm Reibel machine gun was only effective against the lightest armour at a very short distance because its AP-bullet could just penetrate eight millimetres of armour at fifty metres, several efforts were made to provide some more serious antitank-capacity to AMR units. The first was to uparm the main production run vehicles with a heavier machine-gun. The second was to fit the vehicles with the 25 mm antitank-gun; to this effect both a tank (the ZT 2) and a self-propelled gun (the ZT 3), were developed. The 25 mm gun vehicles were primarily intended for the reconnaissance units, the Groupes de Reconnaissance de Division d'Infanterie, of the motorised infantry divisions; these were part of the Infantry, but the Cavalry provided the reconnaissance elements. On 22 July 1936 it was decided to assign four of such 25 mm vehicles to each GRDI. The decision to design two types, despite the very small production batches, was motivated by the desire to let them operate in pairs; the low inconspicuous self-propelled gun would directly ambush enemy vehicles and the higher tank, fitted with a radio set, would be more behind in an oversight position, also with its rotatable turret covering the flanks. However, the Cavalry at first also intended to eventually acquire the ZT 2 for the other AMR units; the general failure of the AMR 35 project ended these plans. AMR 35 à mitrailleuse 13,2 The heavy machine-gun vehicle featured the Modèle réglementaire AVIS-2 turret fitted with a Hotchkiss 13,2 mm Modèle 1930 mitrailleuse, which could penetrate 20 mm steel at 500 metres. To accommodate the larger machine-gun, the turret was made higher, more so at the left where the commander/gunner was seated and from which side the gun was fed — normally this was done vertically, but to reduce height the gun had been rotated to the left — giving it an asymmetrical and skewed appearance. This heavier type was produced parallel to the 7.5 mm machine-gun vehicles of the first production batch in a quantity of eighty; it was originally seen as the normal combat version, four of which would be present in a platoon of five. Later however, production was discontinued: though in 1934 even many battle tanks had been so lightly armoured as to be vulnerable to 13.2 mm fire, such