A: Gustav Gun

The largest gun ever used in combat is generally accepted to be the German "Gustav Gun" built in 1941 by the Krupp company. It had an 80 cm bore (31.5") and fired either a 10,500 lb HE projectile (which made a crater 30 feet wide and 30 feet deep) or a 16,500 lb concrete piercing projectile (which would penetrate 264 feet(!) of reinforced concrete). The typical powder charge was about 3000 lb of powder. The range was between 23 and 29 miles and the muzzle velocity was about 2700 f/s. The gun weighed 1344 tons and had a crew of 500 men. It was used in the German's during the siege at Sevestapol in April 1942.

This is the Carl Gustav m/84 AT-rifle or Granatgevär. Used when assaulting enemy strongpoints or establishing beacheads but also effective against small boats. Full speed ahead with as much led and explosives on target as possible, that's what it's all about and here the Carl Gustav is excellent for fast, mobile, support.

who needs it when you running on rails.