12-pound Howitzers were the same caliber as their big brothers the 12-poound Napoleon, that is they both fired the 12 pound ball. but the howitzer weighed about 1/3 less than the Napoleon, a savings of metal as well as the horseflesh to tow one of these things around. The difference was made up by the size of the powder charge. As the tube walls of the howitzer were thinner and had less mass the full-size Napoleon, the howitzer simply used a much reduced powder charge, lessening the pressures on the tube but also reducing the effective range of the gun. The trade off was between weight, available resources (bronze and battery horses) and range.