When both of those guns were made, the 2 1/2-inch .410-bore shells carried a load of 3/8-ounce of shot.
Super-X .410 3-8 oz. 7 1-2 Chilled Shot.jpg
A few years after the 3-inch .410-bore shell was introduced our North American ammunition manufacturers upped the 2 1/2-inch .410-bore shell to the 1/2-ounce load we all know.