Standard Bayonet Lug forged design
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.
Technical Specifications:
- Height: F-height, compatible with flat-top receivers. May or May Not be marked
- Material: Forged steel for maximum strength and durability.
- Gas Journal Fitment: For .750-inch barrel gas journals.
- Includes: Front sight post hardware.
- Sling Loop: Installed
- Site Pin: Included, along with detent and spring
- Lug: Milspec bayonet lug
- Installation: Must be drilled and taper-pinned into a virgin barrel.
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.
For complete installation, you will need to add:
- AR15 taper pins, to be drilled and reamed in place
- gas tube and roll pin
- handguard end plate (depending upon build)
