Red not dead, the pak40 a 75mm was not avaible in 1941. The gemran infantry marched into russia with 28mm and 37mm ATG's. The first big caliber ATG in widespread use was either rebarreled FRussian 76mm feild guns or Pak 38 50mm in dedicated anti-tank units.
It looks to be around 560mm which is not a real Long rod penetrator by Western standards where the leangth is in excess of 700mm and as high as 850mm.
I was speaking of the Pak 38 - 50mm widely available and really good for close AT purposes. And the Pak 36 (r) only hit the shelves by late 1941.