 Although, other reports suggest that the towed 240 mm mortar M240 were used instead.And OSCE observers, monitoring movements of equipment in the War in Donbass with an UAV, spotted a 2S4 on territory under control of the Donetsk People's Republic on 4 July 2015.The 2S4 Tyulpan designs is based on the GM-123 chassis carrying an externally mounted M-240 240 mm breech-loading mortar on the rear of the hull.