The Magpul MBUS Front is a folding polymer back-up iron sight for AR-15 and M4 rifles, clamping to any MIL-STD-1913 Picatinny rail.
The Magpul MBUS (Back-Up Sight, MAG247) front folds flat against the rail to clear your optic, then springs up positively at the push of a button when you need irons. Molded from impact-resistant polymer over a steel-reinforced core, it shrugs off knocks that would bend aluminum sights while adding almost no weight to the rifle.
The front sight post is fully adjustable for elevation with the same tool used on standard A2 front sights, so zeroing is familiar and quick. It is the sensible, affordable insurance every optic-equipped carbine should carry.
How It Compares
This original MBUS is the light, low-cost polymer option. The MBUS 3 Front Sight is the updated generation, while the MBUS Pro Front Folding Sight is the all-steel version with a much slimmer folded profile.
Key Features
- Spring-assisted deployment: flips up positively at the push of a button
- Folds low: clears optics and co-witnesses with most red dots
- Impact-resistant polymer: tough, light, corrosion-proof
- A2-standard elevation: familiar front-post adjustment and zeroing
- Four finishes: Black, Flat Dark Earth, Stealth Gray, Olive Drab Green
Compatibility & Fitment
Clamps to any MIL-STD-1913 Picatinny rail on AR-15/M4 pattern rifles, including flat-top uppers and railed gas blocks. You need enough clear rail at the front and the right height relationship with your rear sight. Pair it with the MBUS rear (MAG248) for a complete folding sight set; front-post elevation is set with a standard A2 sight tool.
What's Included
- Magpul MBUS front sight
- Integral rail clamp and cross-bolt
Technical Specifications
Platform | AR-15 / M4 |
Type | Folding back-up front sight (BUIS) |
Material | Impact-resistant polymer over a steel-reinforced core |
Finish | Black, Flat Dark Earth, Stealth Gray, Olive Drab Green |
Mount Interface | Picatinny / MIL-STD-1913 |
Adjustment | Elevation (A2-standard front post) |
US Shipping & Support
Shipped from D&R Sports Center in the USA with fast, tracked delivery. Questions on fit, mounting or which model suits your setup? Our team is glad to help before and after your purchase.
Frequently Asked Questions
Will the MBUS Front fit my rifle?
It clamps to any MIL-STD-1913 Picatinny rail on an AR-15/M4 pattern rifle, which covers flat-top uppers and railed gas blocks. Check you have enough clear rail at the front once your optic and any light mount are in place, and that the height relationship with your rear sight works. If your handguard is M-LOK with no rail at the front, you will need a rail section there first.
What does a folding backup sight actually do?
It sits folded flat against the rail so it does not obstruct your optic, then springs up positively at the push of a button when you need irons — an optic failure, a dead battery, or a close-quarters shot you would rather take on irons. The MBUS folds low enough to clear an optic and co-witness with most red dots. Being molded polymer over a steel-reinforced core, it takes knocks that would bend an aluminum sight while adding almost no weight.
How does it compare with the MBUS 3 and the MBUS Pro?
This original MBUS is the light, low-cost polymer option. The MBUS 3 is the updated generation, while the MBUS Pro is the all-steel version with a much slimmer folded profile for shooters who want metal.
Is fitting and zeroing straightforward?
Yes — the rail clamp and cross-bolt are integral, so you slide it on to the rail at the position you want and tighten the cross-bolt. Front-post elevation is set with a standard A2 front sight tool, exactly as on a fixed A2 sight, so zeroing is familiar. Pair it with the MBUS rear (MAG248) for a complete folding set, setting windage on the rear and elevation on the front.
