The F-height Forged Front Sight Block (FSB) was developed as a crucial upgrade during the U.S. military’s transition from the carry-handle rifles of the M16A1 and M16A2 to the flat-top receivers found on the M4 and M16A3/A4. This taller front sight block ensures proper alignment with modern detachable rear sights and optics, offering the additional height needed for accurate co-witnessing. Originally marked with an “F” to distinguish its height, many modern FSBs no longer carry the marking but still meet F-height standards, making them ideal for any flat-top AR platform.
This F-height FSB fits barrels with a standard .750-inch gas journal and comes with all the necessary front sight post hardware. It’s a forged piece, designed to deliver long-lasting durability and performance, especially for demanding tactical and shooting environments. Whether you're building an AR-15, M4 clone, or upgrading a modern tactical rifle, this FSB offers an essential component for proper sight alignment on flat-top rifles.
Important Note: This front sight block is not pre-drilled for taper pins and requires installation by a qualified gunsmith. Since the FSB must be drilled and pinned into place, it is critical to ensure proper alignment and fit during installation, particularly when working with a virgin barrel that has not been pre-drilled for taper pins.
This F-height FSB is perfect for anyone seeking to replicate military-correct rifles or enhance the accuracy and reliability of their flat-top AR-style platforms, ensuring proper sight height alignment with modern rear sights or optics.
CMMG
CMMG
