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Kel-Tec RDB-S Carbine Review

The design of the Kel-Tec RDB-S carbine is outside of the traditional box, but it performs well and is a solid survival gun.

Kel-Tec RDB-S Carbine Review
The Kel-Tec RDB-S rifle is a fantastic long arm for a bug-out gun and for motorcyclists.

“What the %#@! is that?”

“Is that a rifle?”

“That is the ugliest gun I have ever seen.”

“Is that real, or is that a movie prop?”

“How are you supposed to hold it?”

“How do you check the chamber for clear and safe?”

“Thinking about it hurts my head.”

While the Triumph Street Scrambler is not a true enduro motorcycle, it can make an acceptable, lightweight, maneuverable bug-out vehicle if properly equipped. The compact and slim RDB-S is a great match for it.

The previous questions/statements were actual words straight from my friends’ mouths upon seeing the Kel-Tec RDB-S for the first time. Some were long-time gun enthusiasts, and some were casual observers of firearms esoterica. And I heard many variations of the first inquiry, mostly unprintable. In the marketing and advertising world, eliciting a strong reaction is what you are seeking (the fact that these folks had never seen this design before, despite it being on the market for several years, is something else entirely). Good, bad, or otherwise, a strong reaction is never the less memorable. Do you remember where you were when Chrysler first introduced the K-car? No, me either. It was the platform that saved Chrysler from bankruptcy in the 1980s, but it was entirely forgettable. The Tucker Torpedo? Way outside the box. Laser discs? Outside the box. Google Glass? Yup, that too. Of course, those three were mostly abject failures, but…In a gun world vastly overpopulated by AR clones (a design itself that was waaay outside of the box in 1956) churned out by boutique AR manufacturers and large, typically staid corporations that want to be boutique AR manufacturers, I am pleased to see that someone is willing to roll the dice and take a risk on something different. That the someone is Kel-Tec CNC Industries Inc. of Cocoa, Florida, should come as no surprise. Kel-Tec has been eliciting strong reactions in the firearms community since its inception in 1991.

The Kel-Tec RDB-S is a fine choice as a survival rifle in bug-out scenarios. The Spitfire 3x optic by Vortex is a nice match.

The same is true of its founder and head designer, Swedish immigrant George Kellgren. This is the guy behind most of Kel-Tec’s designs. He is also the guy responsible for the infamous Interdynamic KG-9 and Intratec Tec-9 lines of military-styled pistols and the Grendel pistol. (Keep an eye out for an article about the KG-9 in an upcoming issue of Firearms News.) George has never been afraid to take a risk. He is definitely an “outside of the box” kind of guy. When he created the concept for the “Rifle, Downward ejecting, Bullpup (RDB),” he was just following through with a design career that has rarely seen the inside of the box. To call Mr. Kellgren the Swedish John Browning may be a bit of hyperbole, but it drives home the point that the man can and has designed a cornucopia of innovative weapons.


Perhaps the most thought-provoking commentary offered by first-time observers of the RDB-S originated with one of my most thought-provoking friends: fellow instructor, Marine veteran, and astute intellectual Cain Maxwell. Cain stated upon first holding the little Kel-Tec, “That’s crazy. What question does it answer? What problem does it solve?” Indeed. What problem does it solve?

The bullpup design is certainly not new or unique. A bullpup carbine generally refers to one that has its action and magazine situated aft of the trigger assembly. While the origin of the term “bullpup” is murky at best, it appears as though the concept can be, at least, traced back to the Thorneycroft carbine of 1901. When Kel-Tec released the RDB17 for widespread distribution in 2014, it was generally well received, but not considered to be ground-breaking. In 2016, Kel-Tec released the RDB-C. While rumor has it that the “C” stood for “Communist,” I have been told that it actually stands for “California.” Six of one, half dozen of the other.


The “C” model RDB was manufactured without accoutrements of ill-intent, such as a flash hider and pistol grip. It also shipped with a benign 10-round magazine so that it could be possessed in states that choose not to recognize the Bill of Rights. However, it was the lack of a pistol grip that truly made the RDB-C so… unique. It was a design feature that simply could not be overlooked. It was the focal point and the lightning rod, and it could not be ignored. Modern sporting rifles are supposed to have pistol grips, right? Now, old George Kellgren could have stopped right there with the innovation, but being a dice roller from way back, he doubled down on the concept. In 2017, Kel-Tec released the RDB-S. The “S” stands for “Survival.” And that brings us back around to the question, “What problem does it solve?”


The RDB-S is incredibly compact.

Sure, the RDB-S is also a somewhat blue-state friendly platform, but that is not actually the reason for its existence. While the “C” model was certainly politically correct, it was also recognized as being very svelte. From top to bottom, it only measured 4.6 inches, and it was only 1.8 inches wide. Kel-tec decided to capitalize on those slim dimensions by redesigning the “C” as an outstanding survival gun. First, it maintained those external dimensions, but cut the RDB-C’s 20-inch barrel down to 16 inches (the RDB17 is 17 inches). Kel-Tec engineers then modified the barrel profile to pencil-like dimensions to cut additional weight. In a further weight-saving move, they lightened the bolt carrier and adjusted the spring to maintain reliability. They then threaded the barrel, but did not include a muzzle brake or flash hider in order to keep the platform short. Add in some permanently attached folding sights and an adjustable stock (more on both of those later), and BAM, you have what should be considered an exceptional survival platform.

While a motorcycle makes far from ideal cover, it makes a great rest for shooting accurately at extended ranges.

To me, that is the problem it solves and the question it answers: What is the lightest, smallest carbine possible for survival situations? Besides being very narrow in width and short in height, it is only 24.75 inches long with the stock collapsed. It also only weighs just a tad over five pounds (one pound less than the RDB17 and two pounds less than the RDB-C)!

The Vortex Spitfire 3x is a durable, cost-effective optic to put on the top of any intermediate-range rifle.

Other than ruggedness and reliability, weight and size are absolutely the driving factors in the ideal survival rifle. If I need to “bug out” on foot…or by small plane…or by motorcycle, I want a firearm that is compact and lightweight. In a survival situation, space and weight are both at a premium. Military personnel, ultra-marathoners and survivalists all know this to be a fact: ounces equal pounds and pounds equal pain! You don’t think that is an issue? Put on a 40-pound backpack and traverse the steps in your house or apartment building 20 times. Now do the same with a 60-pound backpack, and tell me you don’t recognize a difference. Heck, thru hikers on the 2,200 mile Appalachian Trail are famous for cutting the handles off their toothbrushes just to save themselves from carrying a few extra grams!

Additionally, the RDB-S is manufactured in one of the most popular calibers in the world. 5.56 x 45 or .223 Remington ammo can be found just about anywhere. And, as you well know, the round is ideal for medium-sized game and two-legged predators. It also utilizes STANAG AR magazines, the most common magazine in the western hemisphere.

The bolt catch is ambi, while the mag release is not.

I mentioned earlier that Kel-Tec has elicited strong reactions from its customers and those in the industry for a long time. One of the negative comments you will often hear is the difficulty of being able to find its more popular products, particularly after they are first released. This is what happened with the RDB17. And the KSG. And the Sub 2000. And the list goes on. While doing research for this article, I had the opportunity to interview Kel-Tec manufacturing engineer Joe Easter. Joe has been with Kel-tec since 2014, and is not only responsible for the RDB line, but he is captain of the Kel-Tec shooting team. As a matter of fact, he was gracious enough to submit to my inquiries while he and the Kel-Tec team were in transit to a 3-gun event. (On a side note, because I know you all are curious, the team uses the RDB17 for the event, but as Kel-Tec does not make a full-size pistol, they are free to use whatever they wish. The same goes for a shotgun, as the KSG is not a good choice for 3 gun. They also run Sub 2000s in USPSA Pistol Caliber Carbine/PCC competitions.)

The trigger on the RDB-S is unexpected and exceptional.

Joe acknowledged the problem with them being able to produce enough product in the past. This was partially intentional, as George Kellgren liked to test the waters with new products before fully committing to the market. But Joe said all that has changed. Currently, the RDB line is capable of producing 2,000 weapons per month, but is operating at about half to two-thirds of that. Additionally, he said that they are currently at a capacity of 500 parts per day across the line for the RDB, more than allowing them to keep up with assembly. Joe also said that the new company policy is to have 1,000 units on hand prior to the release of a new product in order to better meet demand.

An adjustable stock on a bullpup is rare and keeps the Kel-Tec ahead of the BATFE.

Out Of The Box

As stated, there is no getting around that pistol-gripless grip. It draws the eyes like a skirmish at a Walmart check out line. And much like that toothless, polyester-clad debacle, you struggle for just a moment to make sense of what you are seeing. Picking up the RDB-S gives similar contradictory feelings of “this is weird” and “I kind of like this” — just like that fight over the last Toblerone that you know you shouldn’t gawk at, but somehow you just can’t pry your eyes away from. But unlike big-box store fist fights, there is a certain sense of competence and quality about the RDB-S…once you figure the gun out.

The rear sight is like an old friend.

As a downward-ejecting bullpup, it took me just a second to locate the chamber to determine if the subject of my pending review was clear and safe. The controls are mostly entirely familiar, if unexpected on a bullpup that looks as if it just came from the set of Battlestar Galactica. The safety is in the same place and works the exact same way as it would on your dad’s Remington 870 shotgun, which means it is not ambidextrous. The charging handle comes from the factory located on the left side of the barrel and will make any Heckler & Koch aficionado feel right at home. The handle is folding; non-reciprocating; locks to the rear in a cut out under the Picatinny rail; and is entirely ambidextrous with a few minutes of your time and a quick glance at the owner’s manual.

The small magazine release is also non-ambidextrous and is comprised of a simple, round button without any type of fence or guard. The bolt-catch mechanism, which certainly does not look like the bolt-catch mechanisms you are probably used to, is ambidextrous and located just above and forward of the magazine release. The two-position stock, highly unusual on a bullpup design, also takes a minute to figure out, but is actually very straight-forward. Just pull the entire mechanism rearward without engaging any type of release, and let it move approximately 1.25 inches to the conclusion of its travels. Collapsing the stock involves pressing in on a stamped steel tab hidden inside the polymer, integral buttplate. You may be asking, with only 1.25 inches of travel, why even bother with an adjustable stock? Great question. The answer is to legally manipulate nonsensical BATFE rules! According to federal regulations, rifles must be at least 26 inches in length. As a survival rifle, Kel-Tec thought it would be prudent to keep the RDB-S as short as possible. With the stock collapsed, it measures 24.75 inches. That extra 1.25-ish inches of travel brings the overall length to 26.1 inches.

The front sight is fragile and too complex.

Anyone familiar with Kel-Tec’s products will instantly recognize the look and feel of its polymer. My example was olive green in color; matte finished without flaws; and small, molded in blocks for extra traction on the handguard and grip. All metal surfaces were finished with a uniformly colored, semi-gloss black. You AR fans will be disturbed to hear that other than the top rail, there are no accessory rails, nor any way to attach accessory rails. No quad rails. No Key Mod. No M-Lok. No place to hang your laser, bipod, vertical grip, coffee cup or night light. Remember, ounces equal pounds and pounds equal pain.

And that brings us to a pain point. Without an accessory rail, there is no way to mount a sling swivel. That normally would not be a problem, as most modern sporting rifles are absolutely festooned with quick-release sling mounts. But not the RDB-S. No sling swivels. No quick-release mounts. No way to attach a single-point sling. When I addressed this question to Joe Easter, he told me that George Kellgren is a big fan of two-point slings using the old H&K-style snap hooks. This is why the majority of Kel-Tec long guns, including the RDB17 from which the RDB-S was spawned, have mounts for such a sling.

A lightweight, compact carbine is essential in a survival situation.

Not so with the RDB-S. In the spirit of less is more and stuff gets really heavy when you have to carry it for a long distance, Kel-Tec eliminated even those simple luxuries. The RDB-S simply has a slot cut in the front of the handguard and the bottom of the buttplate through which an old school sling can be threaded. The slight problem with that is the slots are one inch wide, while the sling provided by Kel-Tec with the firearm is 1.25 inches. Additionally, the supplied sling has the aforementioned H&K-style hook sewn to one end, which will definitely not go through the slot. Not a huge “whoops,” but “whoops” indeed.

Speaking of pain points, let’s talk about the sights. The carbine has a sight radius of 11 inches, which is more than acceptable for accuracy on this type of platform. The front and rear are both metal and folding in nature. Much like the “old-fashioned” safety, the rear sight is a peep on a post that is really reminiscent of the Lyman tang-mounted peep on my Marlin model 1897 that I inherited from my great-grandpa. It has a drum-style windage adjustment knob on the right side held in place with a spring-loaded detent. It is a simple and functional setup that I like quite a bit. And it is of the proper height for a true co-witness with an optic.

Field stripping is straight forward.

Oh, but that front sight! Other than the grip, this is the feature that the eye is drawn to if the sight is flipped up. And the Rube Goldberg nature of the assembly creates almost as strong of a reaction. It is actually a bit hard to describe. However, my biggest problem with it is the complete lack of durability. This is the biggest flaw on the rifle, in my opinion. The first time I took the rifle out of the box, the front sight caught on the cardboard, and my gentle tugs to extricate it caused the assembly to come off of its hinge pin, allowing it to sit askew at the end of the barrel (and this happened two other times while the carbine was in my possession). Believe me, I often prescribe to the bigger hammer method of home repair and I have even been known to strip quite a few bolts, but I try to be a bit gentler with review firearms; at least until I get them to the range. Fragility is not an admirable trait in a survival gun, and I consider iron sights to be a requirement on those platforms. Optics and batteries both fail, but a quality pair of iron sights will keep you in the fight.

Just behind the front sight assembly is a gas-adjustment knob. This is a great feature to have, as it allows you to regulate gas flow to accommodate various loads or when running a suppressor, or if you are that guy who runs his weapons until they are spectacularly dirty. Most ARs are set up over-gassed to enhance functionality, but that is not necessary with the RDB-S. At the factory, the rifle is test fired and the gas adjustment is set for M193 rounds. I never had to touch the adjustment, regardless of what I fed through the carbine.

The RDB-S with its 16-inch barrel is the same length as the Galil pistol with an 8.3-inch barrel.

The barrel is made from 4140 steel treated in a salt nitride bath. Joe Easter informed me that early on in production, Kel-Tec used an outside source for its barrel blanks, but now most of the barrels are made in house. The barrel is threaded at the end and terminates with a very sparse thread protector. In theory, you can run muzzle brakes, flash hiders and suppressors on this weapon, but it is not easy. Elsewhere it has been reported that you can simply remove the thread protector and replace it with a thread extender, so you may use whatever accessory you wish. However, Joe does not recommend that option. He says the best thing to do is to remove the entire front-sight assembly in order to run accessories, and that is not entirely simple to do. You must first call the factory and order a proprietary spanner, which will allow the removal of the assembly. If this were my firearm, I would do exactly that and replace the existing front sight with a high-quality, rail-mounted folding sight.

One of the most interesting features of the RDB-S is that most of its components are interchangeable with the other models in the RDB line. This is evidenced by the fact that the lower polymer assembly is marked “RDB-C” instead of RDB-S. But just in case you were thinking about swapping out the RDB-S’s lower assembly with that of the RDB17 so you can have a traditional pistol grip, don’t even think about it! Not that it isn’t possible, because it is from a functionality point of view. The problem is doing so will cause you to become a felon in possession of an unregistered NFA weapon in the eyes of Big Brother.

The RDB17 assembly, with its non-adjustable stock meant to accommodate a 17-inch barrel, will make your new franken-RDB shorter than 26 inches overall. Swapping out components is simple, as takedown of the firearm is simple. The various major components are held together with four identical pins that can be pushed out with the tip of a cartridge. Be warned: The manual states that the pins are captured, but they absolutely weren’t on my test model. Removal of two pins allows for the removal of the bolt, BCG, spring, and piston. Removal of the third pin allows for the entire lower assembly to be separated. Removal of the fourth pin allows for the removal of the handguard, charging handle and gas assembly. Reassembly is just as easy and tool-free.

At The Range

Once you get the RDB-S out to the range, one of the first things you notice is that the little carbine handles really, really well (after you get over that grip). In fact, the adjective that best describes this gun is “handy.” It points and swings incredibly well. It is just so light and short. I was reminded of just how compact it is when it was laying on the ground side by side with my IWI Galil Ace Pistol. They are almost the exact same length, and the Galil has an 8.3-inch barrel and a stubby stabilizing brace instead of a stock. When I quit fighting the grip, I found that it also suited my natural point of aim.

Regardless of the bullet weight, the RDB-S shot them exceptionally well.

It balances about an inch behind the trigger guard, giving it just a touch of a butt-heavy feel. With it being so light and short, it’s extremely easy to manipulate with one hand. And while the manual of arms is very different from an AR platform, it is easy to manipulate once you figure it out, even though the non-ambi mag release is not ideal. However, the placement of the mag release, the convertible charging handle, and the downward ejection make it a great choice for lefties. I prefer a very tight, CQB-style hold on my long guns, so I often ran the RDB-S with the stock collapsed; not a problem at all for my 6'1" frame. The firearm ran flawlessly straight from the box, without a single hiccup. Okay, one hiccup: I had one failure to fire with a Fusion MSR round, but it was a strong primer strike and it appeared to be the fault of the ammunition, not the gun.


The gun is not meant to be used in a sustained firefight, as the thin barrel heats up very quickly under the handguard. A full 30-round magazine caused a very noticeable temperature increase. And rapid, sustained fire detrimentally affected accuracy. Thankfully, this is not meant to be lugged over to the “Sandbox” as a combat weapon. It is a survival weapon, and if your survival situation puts you in a position of sustained combat, you are probably screwed anyhow.

The downward ejection was a real pleasure and made the person on my right even happier. One exception to this is when I was shooting from the prone position. I like to place my support hand under the butt of the weapon, near my right shoulder. This placement caused me to get a handful of piping hot brass. The first time this happened, I was surprised. The second time it happened, I was mad at the gun. The third time it happened, I was mad at myself. It did not happen a fourth time. Apparently, I only have to get punched in the face three times before I learn a lesson. I think this a truth that my beautiful wife of 26 years would certainly agree with.


The gun was fun to shoot, with minimal muzzle rise, despite the lack of a muzzle brake and being slightly butt-heavy. It also shot incredibly soft. According to the manual, that is because, “The RDB-S has a very long bolt carrier travel contributing to a soft and manageable recoil.” Target transitions were super fast, as the carbine points so naturally.

It has been a long time since I have been surprised by the accuracy of a weapon. The last time it happened, it was not positive. I did not expect the RDB-S to be exceptionally accurate with its thin barrel. I also kept envisioning the RDB-S as more of a PDW than a full-size carbine with a 16-inch barrel and intermediate rifle cartridges, due to its compact nature. Testing proved me wrong, as accuracy was exceptional! Even with me shooting it. Much of that can be attributed to the incredible trigger. It is very light with minimal creep and no overtravel. The manual states that the trigger pull is 6.9 pounds, but I knew from the first time I dry fired it that the trigger on my example was much lighter. My Lyman digital pull gauge showed me an average of around 2.4 pounds! Not at all what I expected from this gun. By the way, the beautiful trigger pull is mostly lost on the user the first time the rifle is dry fired, as dry firing produces a sound and vibration akin to a clanging pot and pan that reverberates through your skull. Really.

But back to the accuracy. I fired all groups from the prone position, using only a backpack for support and a Vortex Spitfire 3X optic at 100 yards. While the Spitfire is a great choice for topping this carbine, it is hardly the best piece of glass for showcasing accuracy. I fired two, five-round groups of each of three different types of Federal ammunition. The bullets ranged in weight from 50 grains to 73 grains. I always give my group measurements as both five-round groups and four-round groups; I remove the flyer in an attempt to take my extreme humanity out of the equation. Regardless of the ammunition used, the RDB-S produced four-round groups of right around 1.5 inches! Not bad at all for a compact, lightweight survival rifle!

Is it the perfect survival gun? There is no perfect survival gun, because everyone has different needs to theoretically survive in different environments and situations. Sustained urban combat would call for a different platform, as would bugging out through Alaskan bear country. But it is a damn good option. I would certainly consider it as a strong contender to stow on my Triumph or in my backpack. I do consider the price tag to be a bit steep in this era of rock-bottom AR pricing, but it is a niche weapon that should have strong appeal within certain market segments. Its strong performance at the range certainly appealed to me, and it should appeal to other like-minded individuals. Being outside of the traditional box, it is definitely one of those platforms that you need to shoot to appreciate. Only time will tell if the Kel-Tec RDB-S will be the next Apple iPad or the next BetaMax.

Kel-Tec RDB-S Carbine Specs

  • Type: Short-stroke gas, rotary bolt
  • Caliber: .223 Rem/5.56x45mm
  • Capacity: Any STANAG AR Mag (20-round magazine supplied)
  • Barrel Length: 16.1"
  • Twist Rate: 1:7"
  • Overall Length: 26.18" (stock extended), 24.75" (stock collapsed)
  • Weight (unloaded): 5.0 lbs
  • Sights: Proprietary metal folding
  • Trigger: 2.4 lbs.
  • Stock: Slightly adjustable
  • MSRP: $1,456 (commonly available for around $1,100)
  • Warranty: Lifetime
  • Manufacturer: Kel-Tec CNC Industries, Inc.

Kel-Tec RDB-S Carbine Accuracy Results


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