FAB Defense Backup Sights RBS & FBS

My .50 Beowulf bear defense carbine got a set of back-up sights. I had considered a lot of backup sights for this carbine, and I have some of several brands, but the sights I chose are FAB Defense RBS and FBS sights.

My Alexander Arms .50 Beowulf Carbine wearing its new back-up sights

I first saw a prototype of the FAB Defense sights a couple of years ago, and I have been waiting for the final product to go into production. As soon as they were available, I ordered several sets to see if they lived up to the potential I saw in the prototypes.

Backup sights are important for any rifle that uses an optic of any kind. Whether found on fighting carbines carried by soldiers or fine custom bolt-action rifles used by trophy hunters, backup sights have an important purpose; to keep the gun in action even if the optic is damaged or even lost. In combat, a survival situation, or when facing dangerous animals, backup sights could keep you alive. I have heard heartbreaking stories from hunters who spent thousands of dollars on the hunt of a lifetime, only to damage or lose their scopes, ending the hunt or leaving them using an unfamiliar rifle.

Nothing protrudes from the FAB folding sights that could catch on gear.

When I look for a backup sight, I look for a sight that is designed for the type of rifle I will be using them on. They need to be out of the way until they are needed. I want sights that are very simple in design and operation, and I want sights that can take some abuse. Because I have a number of rifles, affordability is a consideration.

The FAB Defense RBS and FBS sights meet my criteria nicely.

The streamlined angles of the sight are designed to deflect blows and prevent damage to the sight.

Both front and rear sight have a low, streamlined profile when folded. They do not have sides or angles that are likely to catch on anything, and are built to cause a blow to the sight from any direction to be a glancing blow. The shape of the sights remind me of the armor of a modern tank.

The sights are built strong, from reinforced polymer that, according to FAB Defense, exceeds MIL-SPEC strength requirements. The polymer also keeps the sights very light, adding very little weight to the rifle.

Despite its robust construction, the polymer FBS sight weights less than an ounce.

Polymers today are very strong, and when the correct polymer is chosen for the intended purpose, they can be as good or better than other materials for that purpose. Consideration must be given to the strengths and weaknesses of any material used when designing a product, and this consideration clearly went into the design of the FAB Defense backup sights. The polymer parts of the sights are very robust and the operation of the sight is simple. There are few moving parts, which lead to the more delicate construction of some other backup sights.

The FAB backup sights have no delicate locking system, making the sights simpler and stronger than sights that do.

The cleaner, simpler design leads to both better durability and easier operation. To use the sights, simply push up on the sights and they snap into position. To fold the sights, press back on each sight and they snap back into the folded position. The sights are held in the upright position by a strong detent under spring pressure. There is not lock to lock the sight in either the upright or folded position. If the sights are deployed and they strike an object, the sights simply fold – there is no locking system to break.

The FAB Defense RBS, the rear folding sight, is adjustable for windage. The windage drum is finger adjustable from both the right and left sides. The adjustment clicks are very noticeable for easy counting, and it takes some force to turn the drum, so it will not be accidentally moved once zeroed.

The default aperture is large for CQB and low-light shooting.

Like any standard A1 or A2 M16 or AR-15 sight, the RBS has both a large and fine aperture, with the large aperture intended for close-quarters combat and low-light use and the fine aperture ideal for more precise work. Flipping the large aperture forward brings the fine aperture up into position.

The FBS (front flip-up sight) is finger-adjustable for elevation. A protected adjustment wheel raises or lowers the front sight post, a welcome change from sights that require a tool of bullet tip to adjust. As with the rear windage adjustment, the elevation adjustment in the front sight is held in position by a detent that snaps positively into each position, holding zero and allowing adjustments to be counted. The post on the FBS is round and measures .070″ in width. For comparison, my surplus A1 sights are .064″ wide, my Meprolight A1-style night sights are .o80″ wide, and a standard A2 sight post is .070″.

The fine aperture can be flipped up for better precision.

When used on AR-15s, the front sight is the correct height for installing on a handguard rail that is the same height as the rail on the rifle’s upper receiver. In other words, both sights are intended to be mounted on the same plane, on rails of an equal height.

The front back-up sight is only .88 ounces, and the rear back-up sight is a mere 1.o5 ounces, for a total of less than two ounces added to the rifle, or only one ounce if only the rear flip-up sight is used.

At a price of around $34 for the front sight and about $52 for the rear sight, or $83 for a set, the FAB backup sights are very affordable. They will be available in black, OD green, and dark earth, but only black was available when I purchased them.

I am very happy with the FAB Defense RBS and FBS. They are strong, simple to zero and use, very well-made, and totally snag-free. They are completely ambidextrous both in zeroing and deployment, and they look very good on any AR-15 rifle. I am installing a set on a couple AR-15 rifles, a rear sight on several carbines with fixed front sight towers, a sight on a KPOS, and a set on an AK-74 rifle with a VFR-AK rail system.

For more information or to purchase the FBS or RBS backup sights, click here.

Alexander Arms .50 Beowulf AR-15 with FAB defense folding sights.

Front sight folds flat against the rail to prevent snagging.

Windage can be adjusted from either side of the rear sight.

FAB Defense RBS mounted behind Mepro M21 reflex sight

FAB Defense RBS and FBS deploy quickly by simply pushing up on the sight.

If the sight strikes an object, it simply folds instead of breaking.

FAB Defense RBS sight in deployed position.

FAB defense folding backup sight mounted on a .50 Beowulf

The FAB Defense backup sights require very little space on the weapon.

FBS Folded on handguard rail

FAB RBS Backup Sight behind Mepro M21 on .50 Beowulf rifle.

FAB Defense FBS folded. NOtice the low, streamlined profile.