What is the most powerful artillery piece in the world, considering shell weight and velocity of fire?

 It is difficult to determine the most powerful artillery piece in the world, as there are many factors that contribute to an artillery piece's power, including shell weight, velocity of fire, range, accuracy, and overall design. Additionally, different types of artillery are designed for different purposes, and some may be more effective at certain tasks than others.

That being said, some of the most powerful artillery pieces in the world include:

The M777 lightweight towed howitzer, which is used by the United States military and several other countries. It has a range of up to 30 kilometers (18.6 miles) and can fire a variety of shell types, including high explosive, illuminating, and smoke rounds.

The AS90 Braveheart, which is a self-propelled artillery piece used by the British Army. It has a range of up to 40 kilometers (24.9 miles) and can fire a variety of shell types, including high explosive, illuminating, and smoke rounds.

The D-30 howitzer, which is a Soviet-designed artillery piece that is widely used around the world. It has a range of up to 17 kilometers (10.6 miles) and can fire a variety of shell types, including high explosive, illuminating, and smoke rounds.

The M109 Paladin, which is a self-propelled artillery piece used by the United States military and several other countries. It has a range of up to 30 kilometers (18.6 miles) and can fire a variety of shell types, including high explosive, illuminating, and smoke rounds.

Overall, it is difficult to determine which of these artillery pieces is the most powerful, as they are all designed for different purposes and have different capabilities.