The 24" barrel would be the product or service of a completely new manufacturing process created by Mossberg to contribute to more exact shot placement when working with manufacturing unit made ammunition. The barrel is topped with a vented rib and outfitted with a HIVIZ TriComp fiber-optic front sight. Mossberg https://mondo-growkit07396.laowaiblog.com/28577658/5-simple-statements-about-mossberg-590-a1-class-3-explained