The M27 was a version of the T23 project. After many successful testing of the T23E3, the T23E3 went into service in July of 1943 as the M27. Because of their low silhoutes and torsion bar suspension, both T20E3 and T23E3 are roughly compared with the Russian T-34/85 and the German Pzkpfw IV (with the high velocity guns). After the Ordnance Department decide to find a new successor of the already obselete M4 Sherman tank, they made a new tank. It was a low chassis and used the improved torsion bar suspension. The T23 used an unique electric drive system, which meant the engine's power was directly used to power the tracks. Also another interesting fact is that you could drive the T23 via remote control and you didn't need to be in the tank to drive it. Despite his succes in testing, the request to put this design into service as standard tank was rejected and both T20 and T23 design was ever mass-produced. The reasons where simple. Despite of the Tiger tank threath in North-Africa, the M4 Sherman was a pretty good tank. The Army Ground Forces command never see the Tiger tank operating in great quantity, while the M4 Sherman is produced in high numbers. A M4 Sherman can easy destroy a Tiger tank while operating in a big group and with the right tactic of spread the tanks. Therefore, the AGF doesn't want to interrupt the mass production of the M4 Sherman wich can lead to reduced the tank output.