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Shooters can be very pickly when it comes to iron sights.  I know there are guys who can shoot just as well with AK-47 irons or Winchester buck-eyes as they can with U.S. military aperture sights, but most of us have our preferences. For you folks running ARs, FAB-Defense manufactures an excellent set of affordable polymer back-up iron sights known as FBS and RBS. Here’s the G2 . . .

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A set of BUISs is essential for any rifle that’s going to spend time out in the bush. If your rifle is just a range toy or a 3-Gun competition gun, then you probably have other options if your scope breaks, but a bush gun is different. You might be 20 miles away from camp when your scope fogs up, the batteries die, or it falls off and breaks. Fold-down BUISs are mandatory on those rifles featuring top picatinny rails.

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The most important feature I like about the FAB-Defense sights is that they provide a very intuitive sight picture. If you’re familiar with the sights on an M-1 Garand, M1A, M-1 Carbine or Model of 1917, you’ll be right at home with FAB’s sights. I learned on both the U.S. military sights found on M-16A1, as well as on the HK type globe sights, so these two types of military sights have always been my favorites. So the closer a set of BUISs can mimic the traditional G.I. or HK sight picture, the better I like it. The FAB-Defense sights fit that bill.

Unlike a traditional G.I. sight picture, however, the “ears” on the FBS turn inward instead of outward. So in that sense they are more similar to a traditional HK-93 sight picture. But that’s a pretty easy transition to make for someone who shoots well with G.I. sights.

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The FAB Defense sights are teh same height as a standard Ar-15 sight, so they offer an absolute co-witness with an optic such as the Aimpoint T-2 and LaRue mount.

I also appreciate the compact design of these sights. They’ve been designed to have a low, streamlined appearance. The sides are beveled so that there are no sharp edges or corners to snag on stuff. They kind of remind me of the lines on the F-117 Stealth bomber. The shape also allows you to flip the sight up into position using only your thumb.

The FAB-Defense sights are made of a type of technopolymer, which results in an incredibly lightweight set of sights. The RBS weighs 1.5 ounces, and the FBS weighs only .88 ounces. Nonetheless, the manufacturer claims that the sights “exceed Mil-Spec strength requirements,” but obviously, that’s a claim that’s hard to evaluate. Having said that, you don’t need to spend much time with these sights to gain confidence in them.

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The RBS features an L-type flip sight with dual apertures, reminiscent of the M-16 series of weapons. To recap for those of you that are rusty on how the M-16 sights work, here is a quick primer: The unmarked (small) aperture is used for most firing situations. Conversely, the “0-2” (large) aperture on an M-16A2 and M-4A1 is used for short range work – in theory that’s 0-200 meters, but most soldiers will switch to the small aperture for anything over 50- 100 meters.  I always qualified using the smaller aperture, and I typically shot 39 or 40 out of 40 on pop-up quals.

The 0-2 aperture is used only when the rear sight is turned all the way down. When in the down position, the “8/3” (300-meter) mark on the elevation knob is aligned with the index mark on the left side of the receiver. The elevation knob is used to make shots from 300-800 meters; it works simply by raising the rear sight. Using the small aperture in conjunction with the elevation knob, the shooter can, in theory, hit targets from about 300 to 800-meter downrange. Obviously, YMMV.

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To be fair, it’s worth noting that the FAB-Defense RBS does not have the same type of elevation adjustment found on the M-16 sight. The RBS’s similarity is limited to the fact that it features dual apertures in a leaf sight arrangement. On the RBS, the leaf’s default position is a CQB aperture similar to the “0-2” aperture. The RBS can only be flipped down when the L-shaped flip sight is set in the 0-2 position.

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The front sight post is made of steel, and is .07 inches wide. That’s the same as the front sight post on the M-16.

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One thing I really appreciated about the FBS is that the front sight post can be raised or lowered by simply turning a dial that’s protected so it can’t be accidentally knocked out of position. It is held in position by a detent that snaps positively into position with audible and tactile clicks.

It’s a fast system. I could quickly obtain a “rough” sight-in by simply picking out a rock at 50 yards and shooting a round and then using the thumb of my non-shooting hand to rotate the dial until hits are achieved. This could be done without taking my firing hand off the trigger finger. The process is so fast it’s possible to sight in the elevation in less than 30 seconds using this technique.

I’m not aware of any other system that’s as fast as the RBS. As readers may be aware, adjusting the front sight on an AR-15/M-16 requires the use of a tool (typically a 5.56 x 45 cartridge).

I had previously bought a set of the Magpul BUISs, but the RBS and FBS are superior. First, the FAB-Defense sights are lighter. They’re also smaller, as shown in the comparison photos below:

 

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And unlike the Magpul BUISs, the FBS doesn’t require a tool to adjust elevation. I’m not really sure what Magpul was thinking when they thought that a proprietary tool was a good idea, and it goes down as a rare misstep for that venerable company. However, FAB-Defense clearly gets the win.

Like the Magpul sights, the FAB-Defense sights are available in OD green and tan.

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I’ve been running the RBS/FBS for about a year now can recommend them without hesitation, especially for folks on a budget and are looking to save money on their AR build.

Specifications (for both RBS and FBS unless specified below).

Length (Folded): 52 mm (2 inches)
Length (Operational): 30mm (1.18 inches)
Height (Folded): 14mm (.55 inches)
Height (Operational): 42mm (1.65 inches)
Width: 32 mm (1.26 inches)
Weight: RBS = 30 grams (1.06 ounces); FRS = 25 grams (.88 ounces)
Colors: Black, OD green, tan
MSRP: RBS = $52 / FBS = $34

 

Ratings (out of five stars):

Overall Rating: * * * * *
Better than any polymer sights in their price range. Bar none.

 

34 Responses to Gear Review: FAB-Defense FBS & RBS Iron Sights

  1. Joe, good article. Only thing to add are pictures of you actually using the sights when they’re flipped up and a shot looking down the sights themselves, also while flipped up. If they’re so great, show that you’re using them. Maybe info on how well they co-witness with typical optics, like the one you were using in the shots. I like the comparison between the FAB and Magpul; could show them all flipped up, too. Good idea though.

    • Funny you should mention that, because it was my intent to run the article next week …after I had a change to take some more pics with the sights in the up position. I’ll update the article on Monday.

      Update: new pic is up.

      • Does your vehicle have a spare tire? “Hey, with the advancement of rubber technology and my AAA membership, having a spare tire is absolutely laughable these days!”

    • A case could be made by pointing to the millions of bolt action hunting rifles that have never had nor will ever have BUIS. Get BUIS (or more accurately BUPS) if you want them. But, in my opinion, they’re a $100 AR accessory that is unlikely to ever be needed. They’re highly optional.

      • After the countless cases of guys who ruin their hunt by dropping their scopes on their bolt guns and being left with nothing to shoot? Seriously?

  2. Apparently Magpul agrees with you about the proprietary tool, because the MBUS Pro did away with it and now adjusts with a dial with detents.

    On another note, how does the setup on the rifle above work? Is that a red dot cowitnessed with the iron sights?

    • Yes, the sights are the same height as G.I. sights. I should have mentioned that – edit made. Derp. The Magpul Pros are super nice, IMO.

  3. So, is “technopolymer that exceeds Mil-Spec strength requirements” the new marketing-speak for “thick plastic”? 🙂

    • Yeah, I’m not sure what that means, other than its plastic. Works, though. It might break if you used the rifle as a hammer, but it will hold up to normal use.

  4. Joe,

    I’ve read some reviews that described loose/unstable mount issues. I suspect user error on that but I’m curious how tight/solid/stable they have been with continued use?

    Thanks for an informative review

    • I went through buying and returning three sets of these sights about a year ago. None of them fit right, even the ones the importer said were newer production that had corrected the problem. The rail channel was just too wide by design. No amount of tightening would keep them from wobbling. I tried them on several rails from different manufacturers, just to make sure the rail wasn’t the problem. I considered abandoning them, but I was building an under 5 pound AR, and these are about the lightest sights around (the Spike’s Tactical are lighter but not as well designed, fit issues aside). I ended up laboriously filing down the pieces you tighten down until I could get a snug fit. The plastic is very tough, as I learned the hard way. I hope FAB/Mako has resolved the fit issues, because they are nice sights.

  5. I bought a Japanese 7.7 (Type 99) and found its sights my favorites. The rear is a ring, the front is a triangle, and I found that triangle was great in low light, when I couldn’t really see the tip; my eyes instinctively knew where the tip was based on the sloping sides, as opposed to a post, where the end just sort of disappeared.

    The Swiss K31 also has a triangular front post, but the rear is a notch, and not as good as the ring in low light.

    Might have something to do with being somewhat near sighted.

  6. For my build the Magpul sights were a done deal until I read this article. I may need to further explore the FAB sights. Don’t like the idea of a proprietary tool, and the FAB sights overcome this issue for half the price of the Magpul Pros. Hmmmm….

    • So what if the magpul front sight has to have a tool to adjust, honestly when have you ever adjusted the front sight after the initial sighting in. They still look better than the Fab’s. And if you have any storage on the rifle i.e.: pistol grip or butt stock, you can store it in there. Great review though! If you’re on a budget the Fab’s are the way to go, second best looking set I’ve seen. Love the tungsten color, definitely going on one of my ARs. ?

      BUY AMERICAN, SUPPORT YOUR COUNTRY!!

  7. I bought a set of these for my first (and only) AR build. I used them for 6 months until I purchased a red-dot. They now sit folded and ready to go. They are still solid, they are still zeroed. I have a lower 1/3 co-witness for the red-dot, and the FAB sights line up nicely at the bottom of the optic. The detents to lock them in place are solid, there is no rattle or wobbling when they are folded or up. Definitely great sights for the money.

  8. Meh. Buy American; as is, this looks like another cheap POS Israeli knock off of Magpul.

    Buy American originals, not some cheap POS Israeli knock-offs.

      • Yeah, ’cause apparently US armed forces never use MagPul.

        xD

        Yeah, given the option, people are gonna buy Magpul, over ‘FAB’ulous tactical glitter.

        They’re one of the lowest grade polymers in the industry. Rugged use my ass: sounds like you work for their PR dept.

        xD

        • Please provide a cite to back up your statement that “[t]hey’re one of the lowest grade polymers in the industry.” I think you are confusing product lines or manufacturers.

    • The Israeli stuff sees some of the hardest use in the real world, outside of third world crapholes where they never maintain their ex-Soviet hardware.

      If it’s good enough for the IDF, it’s good enough for me. At minimum the rear sight has seen use on surplus M4s, and while they’ve all transitioned to the Tavor/X95, you can bet they vetted these at some point.

  9. I think these will be the BUIS for the build I’m working on. Way cheaper than the Troy or Magpul pros, and having been to Israel I trust the hardware they put on the market.

  10. I can’t say anything about these sights, only that FAB makes some tough plastic. My Vz. 58 has all beaver barf parts and folding stock replaced with FAB Defense parts. I’m very happy with all of them. The upper handguard with attached red dot even keeps zero after being taken off for cleaning and reattached several times.
    I think I will put these on my new ar build. Thanks for the review, I almost bought MBUIS.

  11. I noticed the AFAB on there…a review of the AFAB and EFAB on both 16″ and 10.5″ – 11.5″ (any SBR) would be really nice. I like everything about these two muzzle devices but not sure what the concussion relative to the A2 would be on a 11.5″ barrel.

    Great review on the FAB defense sights, I’ve been looking at these for a while but decided on MBUS Pro rear.

  12. Judging strictly by your photos, these sights still don’t appear to be the right height. They look shorter than mbus and other correct height sights.

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