The final tank destroyer to enter service was the M36. This was a development of the M10 hull with a new turret mounting a 90 mm high-velocity gun, the most powerful anti-tank weapon which would be carried by American forces in Europe. A prototype was originally constructed in 1942, as an experiment, and the design was standardized in June 1944. In July, the European command requested that all M10 battalions be converted to M36s, and the first vehicles reached the front lines in September. It proved more than capable of countering heavy tanks – it was recorded as disabling a Panther tank at 3,200 yards – and its roots in the M10 meant that it possessed greater survivability than the M18. A modification of the M18 upgunned to 90mm was never approved for series production.