In a large bowl, combine ground beef, bread crumbs, onion, milk, egg, salt, Worcestershire sauce, and ground black pepper. Mix together, and shape into meatballs. In a large skillet, heat shortening over medium heat. Add meatballs, and cook until browned, about 5 to 7 minutes. Remove from skillet, and drain on paper towels. Add chili sauce and jelly to skillet; heat, stirring, until jelly is melted. Return meatballs to skillet, and stir until coated. Reduce heat to low. Simmer, uncovered, for 30 minutes.