well liked by some Soviet tankers, while others called it the best tank for peacetime service. When Britain received the tank, it was given the designation Sherman, which gave rise to the name Sherman tank and the UK naming its US-built tanks after American Civil War generals. Both the British and the Soviets re-armed their M4s with their own tank guns. The Soviets re-armed a small number with the standard 76 mm F-34 tank gun but so much 75 mm ammunition was supplied by the US that the conversions were not widespread. Unfortunately, the fairly short-barreled 75mm gun most Shermans came equipped with did not offer very good armor penetration even with specialty ammunition, especially against the then-new Panther and Tiger. However, the British 76.2mm (3-inch) Ordnance QF 17-pounder, one of the best anti-tank guns of the period, happened to fit in the Sherman's turret quite well with a new gun mantlet and sight, and this became a very common modification known as the Firefly. The other main modification was that the radio moved to an armoured box welded to the turret bustle, which also contained the much larger counterweight for the new gun. The combination of British and American weaponry proved desirable, although despite the United States building a few 17-pounder Fireflies from new, it never went into mass production and did not see action. The US had its own 76 mm calibre long-barrel gun for the Sherman. While it wasn't as good as the 17-pounder, it still had a much better chance of successfully engaging German heavy tanks especially at close range, offered consistent kill-power against more equally-matched opponents at all ranges, and didn't require major modification to fit like the 17-pounder did. The Firefly thus remained a British variant of the Sherman. The M10 Tank Destroyer was also up-gunned with the 17-pounder, creating the M10C tank destroyer. This was used in accordance with British tactical doctrine for tank destroyers, in that they were considered self-propelled anti-tank guns rather than aggressive 'tank hunters'. Used in this fashion, it proved an effective weapon. The British also used the Sherman hull for two other Sherman variants known as the Crab, a mine flailing tank, and the DD Sherman, the 'DD' standing for Duplex Drive. The DD was an amphibious tank. A flotation screen gave buoyancy and two propellers powered by the tank's engine gave propulsion in the water. On reaching