Here is a picture of the worlds largest rifled muzzle-loader, located on the island of Malta. It's a 102 ton British Armstrong. It has a 17.72 inch bore and a barrel length of 35 feet and with 450 pounds of black powder it could propel a 1 ton shell eight miles. There's a good story about this gun in the summer '07 issue of the Artilleryman magazine.
Max
