The two-wagon train was originally armed with a WWII German 20mm gun and two 9K11 Malyutka missile launchers; a Bofors 40mm gun was added later. A pair of M-53 7.9mm light machine guns were mounted to defend the blind spots. The 40mm cannon was removed in 1992 and replaced by a Soviet-designed 76mm gun mounted on the rear wagon. The convoy was enlarged with a third wagon mounting two 20mm cannons. Two Zastava M84 machine guns and a twin 57mm multiple rocket were also added in 1992. The following year marked the definitive configuration of the armored train, when the 76mm gun was supplanted by an American M18 Hellcat tank destroyer. There was an open wagon with two 120mm mortars, but their operational use was limited. The end of the war in Croatia frustrated plans of mounting an 88mm flak gun.
The sandbags which provided the first shield to the wagons were replaced by a 25mm thick armor plate. The roofs remained open and were covered with tarpaulins. On the sides the wagons were wrapped in canvas and rubber sheets, the in between space filled with gravel. This improvised laminated protection proved effective in combat when it dissipated the blast of an antitank missile.
During the siege of Bihać three additional wagons were hooked ahead of the formation, in order to trigger any mines planted on the railway. One of the wagons carried tools and materials for railroad repairs if needed.
