Place water, salt, bread flour, dry milk, sugar, and yeast in the pan of the bread machine in the order suggested by the manufacturer. Select Dough cycle.

When the cycle has finished, preheat the oven to 350 degrees F (175 degrees C). Lightly grease a baking sheet.

Roll out dough on a lightly floured surface; shape it into a 16x10-inch rectangle. Transfer to prepared baking sheet.

In a small bowl, mix together chopped pepperoni and mozzarella. Spoon pizza sauce in a stripe down the center of dough lengthwise; add pepperoni and cheese filling. Make diagonal cuts 1 1/2 inches apart down each side, cutting within a 1/2 inch of the filling. Criss-cross strips over filling, sealing with water. Brush top with melted butter.

Bake calzone in preheated oven for 35 to 45 minutes.