It's called a bore evacuator, and its function is to prevent gasses created from the firing of rounds from getting into the turret.
Gatling gun
I don't know the height of the tank. If the tank is 20 ft high, then there is a volume of 25 barrels per ft.
The original Gatling gun had six to ten barrels which rotated and fired independently. This was one of the earliest machine guns made.
Dozens of countries
Part of the sight.
Technically, there is no limit.
SteelSteel
Interior or exterior?
what is the name of the gun on a tank
Any Spyder threaded barrels.
The first ones had six barrels that used .58-caliber ammunition.
Tank is 40 feet high and holds 55,000 barrels.