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Kel Tec RDB: aka Rifle, Downward-Ejecting Bullpup in 5.56

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The Kel Tec RDB is a mind-blowingly short, micro-bullpup chambered in 5.56 and capable of unleashing some serious firepower in a compact space.

Kel Tec Bullpup Carbine For The Rest of Us

You’re staring into the trunk of your Toyota AE86 urban assault vehicle/mobile arms room. A mission just came down the pipe then self-destructed via Snapchat. You’re going to be performing remote brain surgery on multiple hostile targets in a densely populated, urban antique shop. Thankfully you have the Kel Tec RDB.

The environment will require the negotiation of tight corners and expansive corridors. Engagement distances range from bad breath to 200 meters. You can’t remember if you’re right or left handed, so you’ll need an ambidextrous 5.56mm rifle — one that’s low profile and maneuverable, but capable of reaching out and terminally fondling the bad guys.

You’re a badass, but you’re polite. You definitely don’t want errant ejected brass damaging the surrounding fine-china displays. As if that wasn’t enough, the United States has been flooded with cheap foreign goods, and there’s no way you’re further contributing to the relentless influx of heathen communist products. You’re going all American on this one.

Who hasn’t been faced with a scenario like this? What weapon will you choose? Thankfully Kel-Tec has addressed exactly this type of conundrum with the RDB (Rifle, Downward Ejecting Bullpup) — a rifle so interesting and unusual that RECOIL had no choice but to perform a full and thorough evaluation.

So, what exactly is the Kel Tec RDB and how is it different from the slowly expanding list of bullpups that have come out to date? The easiest way to delve into that question will be to focus on its deviation from well-known bullpup designs of the past. Let’s begin with loading procedures.

Kel Tec RDB: aka Rifle, Downward-Ejecting Bullpup

Photography by Natalie Cake

We evaluated the RDB with both the Vortex Razor HD 1-6x as well as a Trijicon TA33 3x ACOG with an Insight Technologies PEQ-15 mounted in series.

We evaluated the RDB with both the Vortex Razor HD 1-6x as well as a Trijicon TA33 3x ACOG with an Insight Technologies PEQ-15 mounted in series.

Kel Tec RDB Modus Operandi: Stuff It And Slap It

The RDB feeds from STANAG magazines in a location behind the grip (duh, it’s a bullpup) and in front of a downward-facing ejection chute. The chute is reminiscent of the ejection port of the FN P90.

It’s also similar to the P90 in that chamber inspection is accomplished by inverting the rifle with the firing-hand and peering into the ejection port while cycling the bolt with the support-hand.

For the uninitiated, clearing the RDB is kind of like kissing your sister — a little awkward at first, but the more you do it, the more you’ll like it.

The end-user will find that charging the weapon is one of the highlights of the RDB experience. You’re going to have plenty of options!

The RDB’s non-reciprocating charging handle is similar to the HK MP5 in function. It can be pulled back and rotated upward to lock the bolt open, then slapped downward to load a cartridge. The handle itself can be swapped from the left to the right side of the weapon during disassembly.

This means that southpaw shooters will finally be able to perform the coveted “charging-handle slap” with their support hand during administrative loading — just like Bruce Willis in Die Hard!

The RDB’s height over bore is a little taller than a typical AR, so mounts like this Warne RAMP take a little getting used to. The good news is that there’s plenty of rail space for a set of low mount rings.

The RDB’s height over bore is a little taller than a typical AR, so mounts like this Warne RAMP take a little getting used to. The good news is that there’s plenty of rail space for a set of low mount rings.

You probably noticed that we wrote “administrative” loading above. We make mention of that because, unlike the MP5, the RDB features a last round bolt hold-open.

It also has an ambi bolt release just above the magwell, at the natural point of contact for the thumb following all types of mag swappery. The bolt release can be used as a bolt catch to lock the bolt open in conjunction with the charging handle, making the manual of arms similar to the Tavor, but with the added flexibility to perform manipulations like an MP5.

Brass to the Grass

We found the RDB to excel at close ranges. The rifle is piston operated and seems naturally balanced and light even for a bullpup, which typically have their weight concentrated toward the shoulder.

The weight and balance contribute to quick muzzle recovery during firing. With minimal concentration, we were able to repeatedly connect on 8-inch (face sized) steel at 40 meters with controlled pairs and half-second splits. The fire selector was a topic of debate among shooters during testing.

Some found the selector to be awkward, requiring repositioning of the firing hand, while some found the selector to be convenient both in its location and 30-degree throw. All found the engagement of the selector was lacking in positivity and mushier than last week’s mashed taters.

The selector definitely engages with more passivity than that of the Tavor, the crossbolt selector of the AUG, or the rotary selector of the AR-15.

The downward ejection of the Kel Tec RDB is an awesome feature. There, we said it. Brass ejects near the shooters armpit and emerges with enough authority to allow fire in various non-standard positions, such as urban prone. Or even completely upside down, which when performed, projects a glorious fountain of brass into the air.

The utility of downward ejecting 5.56mm is only limited by your imagination, but it’ll definitely come in handy during CQB and vehicle mounted firing. The flip side to this is that if you rapidly fire two mags from prone, you’ll quickly find yourself lying on top of 60 pieces of hot brass.

Picatinny rail remains attached to the barrel during field stripping, so no loss of zero occurs. Note position of hammer at rear of lower receiver, contributing to awesomeness.

Picatinny rail remains attached to the barrel during field stripping, so no loss of zero occurs. Note position of hammer at rear of lower receiver, contributing to awesomeness.

Gas adjustment on the RDB is continuous, giving the shooter a great deal of flexibility in how much or little they choose to gas their weapon.

The valve is a traditional drum, located at 12 o’clock over the barrel at the end of the handguard. Gas can be adjusted using a 5.56mm round. We ran an AAC Mini 4 suppressor through most of the evaluation — an especially kick-ass complement to the RDB.

Even during mag dumps, a suppressed RDB will not vomit gas back into the shooter’s face, a pleasant surprise especially after years of shooting the spitting cobra that is the suppressed AR.


The magazine release is a stamped steel push-release lever. It’s actuated with the rear of the firing hand similarly to the Tavor, except that the RDB’s mag release travels linearly rearward instead of pivoting on a fulcrum.

This is an advantage over the Tavor in that unintentional mag drops should be even less likely. During testing, we found that aluminum STANAG mags and Gen 3+ PMAGs functioned flawlessly in the RDB. Gen 2 PMAGs failed to fully seat due to the raised contact points on the rear of the magazine, and several varieties of bananas that were tested didn’t lock in at all because, of course, bananas aren’t magazines.

We tested two RDB samples during our evaluation, a first-draft production model and a prototype. The production model failed to reliably eject PMAGs while the prototype kicked out mags of all flavors. We later learned the prototype had been hand-sanded, so even if Kel-Tec doesn’t address this issue, sand paper is pretty cheap…and we all know that “bitchez love crafts.”

keltec-rdb-bolt keltec-rdb-bottom keltec-rail

The Kel Tec RDB features a 17.2-inch button-cut, 4140, nitrided steel barrel. It’s lightweight, having a minor diameter of 0.560 inch (forward of the gas block) and 0.625 inch under the handguard. The muzzle is threaded ½x28 with a threaded collar, which negates the use of crush/peel washers when indexing muzzle devices.

Kel Tec RDB Review

Firing M855 ball from the supported prone, I averaged about 3.5 to 4.5 MOA five-round groups at 100 meters. (Note: I’m a 34 out of 40 kind of guy on Army qualification ranges.) Another more-refined shooter was able to attain 1.5 MOA groups using Black Hills rounds loaded with 69-grain Sierra MatchKings from the same rifle.

The RDB we tested had a 1:9 twist, but future production guns will be 1:7 which should help stabilize the longer projectiles.

We evaluated the RDB with both the Vortex Razor HD 1-6x as well as a Trijicon TA33 3x ACOG with an Insight Technologies PEQ-15 mounted in series. We experienced zero issues with optic interference on the RDB’s controls and zero malfunctions with the RDB in general.

We love and hate the RDB’s trigger. It’s innovative — many bullpups use crude extension bars to engage the sear, while the RDB contains its trigger and sear in a pack like the Tavor.

Despite the use of a co-located sear and trigger, we found the pull to be unpredictable and sluggish, requiring the user to defeat multiple walls during its course of travel. The trigger is a plastic composite material that adds an element of flex, and when combined with the resistance of the sear engagement, seems to promote vertical shot dispersion.

Kel-Tec informed us that a certain (unnamed) trigger manufacturer may be offering an aftermarket trigger pack for the RDB. Even with the stock trigger, we wouldn’t say it’s bad or worse than other contemporary bullpups on the market.

The Kel-Tec RDB gives the official designation of “firearm” to its stamped-steel receiver cover. This will allow Kel-Tec to offer caliber conversions and other aftermarket OEM parts without the customer needing to modify or replace the actual regulated firearm.

The lower and handguard are made of glass impregnated Zytel, which does a good job of enclosing the rifle, keeping weight low, and protecting the weapon from real-world trauma. After a 90-round string of sustained fire, the temperature of the handguard was no warmer than what you’d expect of any comparable semi-auto.

Any heat buildup that occurs is isolated mostly in the front of the handguard. The RDB has multiple large attachment hoops for HK-style hooks or cord slings. However, there are no QD cups on the rifle. So for the diehard QD fans, you’ll just have to hang lead weights on the gun, which is basically the same thing.


The bolt of the RDB is based on Stoner’s seven-lug, rotating-bolt design with the extractor at the 6 o’clock position. The bolt carrier is inspired by the CETME/HK G3 design, with a single return spring feeding through the back of the carrier and a tappet rod projecting out of the front.

The front of the carrier makes contact with a tappet cup inside the gas block. These components combine to make up the RDB’s inline, short-stroke piston system. Guns seem to love inline design elements, so we think this system is kind of genius.

Next, we should mention the hammer, which is one of the wildest features of the RDB. Kel-Tec went “full Outback Steakhouse” on this — no rules, just right.

The hammer is housed all the way in the back of the lower, behind the ejection port. When it’s released, it pivots over the top of the ejection chute to impact the firing pin. This makes the RDB’s internals super-efficient in their orientation. In fact, much of the RDB’s length is only present to satisfy the NFA’s Orwellian minimum length requirement of 26 inches.

The design itself seems fully capable of being a mind-blowingly short, micro-bullpup.

What Does It All Mean?

The bottom line is that there’s so much crazy-awesome-shit going on inside the Kel Tec RDB with every pull of the trigger, we can’t possibly cover it all in one article.

The mere fact that you could perform charging handle slaps in the mirror while screaming, “Yippee Ki Yay” all day long should convince any sane person to purchase this weapon immediately at any price.

RECOIL gun test of the Kel Tec RDB. Yeah, we had fun.

RECOIL gun test of the Kel Tec RDB. Yeah, we had fun.

Kel Tec RDB is a compact and handy bullpup.

Luckily for you, the Kel Tec RDB is anticipated to retail for around $1,500. With so many manufacturers regurgitating clones of Stoner’s AR-15, it’s liberating to see American companies like Kel-Tec, churning out entirely new designs with every product they release.

I think every shooter should own an AR-15 and an AK variant, but dare I say the RDB may be a close third? We anticipate the RDB to be a highly sought-after KelTec bullpup when it hits store shelves and should probably be purchased on sight. This being Kel-Tec, however, we should probably add the qualifier “if you ever see one” to the end of that sentence.

Kel-Tec RDB Specs

Caliber: .223 Rem
Barrel Length: 17.4 inches
Overall Length: 27.4 inches
Weight (Empty): 6.9 pounds
Magazine Capacity: 30 rounds

Kel Tec RDB Accessories
Vortex Razor HD 1-6×24: $1,900
Warne Ramp 30mm Mount: $188
Magpul MBUS Pro: $190
Magpul AFG: $35

Price as Featured



Also check out the Kel Tec KS7

Corey Graff contributed to this article.

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