 The Leopard 2A6 and its longer L / 55 main gun have been exported for use by the Canadian Army , and the Netherlands upgraded part of its original fleet of Leopard 2s with the more powerful armament . The British Army has tested Rheinmetall 's longer gun , possibly looking to replace the current <unk> 120 mm L / 55 rifled main gun on the Challenger 2 . Two Challenger 2s were modified to undergo firing trials . World Industries Ace Corporation ( <unk> ) , a Korea @-@ based powertrain company affiliated with Hyundai Kia Motors Group , is also producing the L / 55 under license for the new K2 Black Panther , a fourth generation South Korean main battle tank . 
