For any rifle intended for serious use, iron sights are essentially mandatory. Optics are great and are proven to increase hit capability, but they can also fail, and your system needs to include a reliable second option when this happens.
Magpul’s MBUS front sight is a great choice for completing your system with backup iron sights (BUIS). Made from lightweight yet durable polymer, the MBUS front sight weighs only 1.2 oz. It also folds down to fit neatly beneath an optic or other accessories, but the spring-loaded assist helps the shooter deploy it instantly when needed.
The MBUS front sight stands at the same height as a standard A2 sight for compatibility and is also adjustable for elevation. In short, it has all the features you would need in a competent BUIS but its profile is so low that it’s barely noticed. Where ounces count, the MBUS front sight provides backup features without bulk.