I've owned 2 Steyr AUGs and an X95 (I skipped the Tavor since the Israelis only decided to sell it to the US after they had already moved on to the improved version with the X95). However, a guy who often shoots the RFB at the range I go to, showed up with an RDB, and after shooting it, and finding one for $980 OTD, I got one.

After shooting it for myself, breaking it down and looking at the ingenuity in the design, I think it really is a great gun except for a few things. Aftermarket needs to make a good MLOK rail handguard* (I'm not a fan of the one option so far), a tough/ruggedized trigger and trigger group parts (to replace plastic parts), a better (non-plastic) charging handle (non-folding), and PERHAPS an upgraded gas-adjustment knob with numbers, better clicks, maybe only 10-15 settings, with a way to lock it once set (or stronger detents).  
* -- A new handguard would be INSANELY easy to make since it only has one pin holding it on--a company could make them for $50-$60 and sell them for $150!

PROS:  
1)  Very handy. It is lighter and has a shorter LOP than any bullpup I've shot (I'm 5'10" w/ short arms).
2)  17.4" barrel gives a tiny boost in FPS over the 16" AUG and 16.5" X95
3)  Trigger is the best OEM BP trigger I've experienced...though $$$ can make the AUG/X95 good too.
4)  No blowback from firing suppressed and is completely ambidextrous.
5)  Shoots softer and flatter than any BP I've shot.
6)  Very affordable at $900-$1050.

CONS:  
1)  Too much plastic. The upgrades I mentioned would make it a really great gun.
2)  The downward ejection only helps with things that don't matter to me:  ambidextrous usage and suppressed fire; however, it also would allow mud/dirt to get in the gun if you were in a bad environment. For this reason, I don't think it would ever be a good military/hard-use gun. However, for most individuals and even police, I think it'd be great.
3)  Keltec can't seem to keep up with the demand of their guns, and though the designs are ingenious, the aesthetics are often mind-bogglingly ugly. It's like the designer is the new John Browning, except they need someone who understands aesthetics:  the folding front sights on the RDB-S show that they have no idea what is visually acceptable.
4)  Most serious gun people have a stigma (likely deserved) against buying a Keltec despite the lifetime warranty.

The problem is that for the cost of your upgrades, you'd be able to buy a Tavor or AUG and avoid the Kel-Tec stigma.

There goes that whole FPNI thing again. Fukkin amazing how that works.

I don't buy that it would cost the same.  You'd still be saving 1/3rd for a gun that's over a pound lighter, handier (which I care about), and suppresses better.  ** If it doesn't prove reliable, I'll go back to the X95 most likely.  But I sure wish we could get an aftermarket to optimize this platform.  It shoots softer and flatter than the X95 or AUG (both of which are already soft shooters IMO).

$950 RDB
$150 handguard.
$100 trigger and cocking handle.
= $1200

AUG or X95
= $1600
+ $150-$400 in trigger and upgrades (I hear those geiselle triggers can get pricey)
+ $100-$150 longer top-rail upgrades (popular with AUGs)
= $1850-$2100

I'll take the combat proven rifle over the civilian novelty any day.

I have absolutely no problems with my AUG.  Except that I haven't bought any extra mags for it yet.

Comparing Keltec gun design to Browning is absurd.  Keltec can't build a gun without using 2 dozen screws.

1)  The X95 and AUG are both combat proven. I don't need a combat gun for 99.99% of my uses (maybe you do). Of course, if I do, I have combat proven ARs. So I think spending 1/3rd the money for a handier, lighter, smaller gun isn't a bad idea.

2)  As far as John Browning, I was referring to the fact that few American makers are really innovating. KT did the KSG, the RFB/RDB, and even started the .380 pocket thing with the P3AT (quickly copied by Ruger and everyone else). The operating system of the RDB is very interesting. While it's just a short-stroke piston, the trigger and sear design blow away the OEM AUG and IWI bullpup trigger designs (though perhaps it won't prove to be as rugged despite the double-springs in the trigger that remind me of AKs). I hear you can spend $300-$350 and make the X95 very nice via Geiselle. I also prefer the mag-release (I hated the Tavor mag-release, but the X95 is standard fare, and the AUG is easy to get used to).

3)  The tons of screws thing isn't a big deal to me--you don't need to mess with them to break the gun down fully. The CZ Scorpion has the same type thing with tons of screws. I think it's a simple cost-cutting measure that doesn't hurt anything like reliability (the X95 likely has 1/3 as many screws).  Also, the "serialized" part of the RDB is a tiny little metal plate attached to the buttstock--so ALL of the important things could be modular (another innovative idea we haven't seen in carbines as far as I know).

NOTE:  
I would never recommend someone get an RDB if they could afford an X95 AND needed the guarantee that it would run in tougher conditions (of course, a lot of the Tier 1 Israeli units still use ARs/HK416s NOT the X95). But I'm also under no illusion that I'll be running through mud doing somersaults out of helicopters with my RDB.

BUT if someone is looking for a lightweight, less tall, handier gun, with a better OEM trigger, that will do 99.99% of what an AUG/X95 will do--and suppress better, they might should consider it.

Here's my take on the plastic trigger parts - they work. HK proved it with the G36 and .... oh, wait ... aren't the AUG sear components plastic? While HK's G36 has been plagued with issues, and the Germans began actively looking for a replacement after just 20 years of service, the plastic trigger components are not the issue, or even an issue (hint: the barrel is hunting rifle thin, and they still have full auto capability. HKs advice to the Army, was to let the weapon cool between shooting sessions - as if that's always possible in combat?). If the Kel-Tec components are an issue, it may be a material problem, but not all "plastic" is cheap, inferior material that needs immediate replacement. It may be a concern of the type of polymers used, reinforcement material, or the initial design of the part's bearing surfaces. However, just to sweep everything under the "plastic needs to be replaced" rug is an extremely over-simplified viewpoint.

Additionally, replacing plastic with steel is going to add weight and cost, which are some of the things you were so impressed with.

What are you waiting for, then? If it's INSANELY easy, and the profit is so good, why not start making them and get rich?

FIFY

Or you could just buy an M17S and call it a day.

How’s the accuracy and reliability?

What about hot handguards?

OP I agree with you.  The RDB makes an excellent civilian and home defense rifle if you get one that has been QC'd properly.  Be real, you aren't marching through swamps from your bedroom to the front door.  The Kel Tec design is great, it has almost all the right features as well.  I agree on the handguard being one of the largest issues too, but I think we need to go one step further: free float.  The real problem is that with the current design you cannot really free float.  It would be easy enough for Kel Tec to release one that is FFed with a proper handguard though.  Then in addition to HD and CQB, you could have even more fun at longer ranges with one.

If I'm getting dropped into Cambodia, yeah I want a Tavor or AUG, but I won't be in this life.  The RDB would be really fantastic with some aftermarket and a slight redesign AND PROPER QC KEL TEC!

But I like my gutters where they are - on my house.  

+ I bet it heats up under moderate rates of fire.. ?

Excellent accuracy, awesome trigger, eats just about everything, plus there's plenty of surface area for you to cook eggs or steak or whatever you want on.

(it heats up, but not anywhere near as bad as the original; get a VFG or wear gloves)

Re:  PLASTIC:
Yeah, the plastic doesn’t bother me in the sense that it’s weak so much that I’d prefer the feel of an aluminum triggger.
I don’t know, but assume some of the internal parts could be improved with better quality aluminum and steel parts (even the KT aluminum and steel parts/springs).

Re:  Make your own:
It would be INSANELY EASY IF you had the access to the machines, the know-how, and seed-money to build 1000 strong, aluminum mlok hand-guards (which I don’t have, but many people do).  I know one guy did it, but am not a huge fan of his design (which lets the ugly trigger guard just dangle down).  I’ve read Midwest Industries and KT are working on it, but if I could strike first I would. I’ve worked with small manufacturers before (just on design and testing), but I think emailing HBI, Manticore, and GearHeadWorks might be effective IF they realized this was a good gun. Of course, I think the X95 needs more handguard options, but maybe I didn’t look hard enough. I’d also love to find a way to shave a pound off the weight of the X95.  :)

The S is actually a 16" barrel due to that sliding buttplate. The RDB normal barrel is 17" to make the 26" overall.

2) I bought one recently, to try with my silencer when it comes. Supposed to be great for that, though I think it'll still have some piston pop that might make it meh. Ambi isn't a big deal, but not having brass at your ear is a good thing.
3) Kelgren has been around for a long time, all his guns are ugly. Grendel, Keltec, Tec9... It's just his design sensibility I guess. Really the RDB's main aesthetic drawback is the fore-end, which we both agree needs to be replaced with a nice mlok option that's slimmer. :)
4) I've had a P11 and PF9, both worked great. When I worked at a gun shop, I found that most of the small keltec's reliability problems were from folks limp wristing. They always had a rep for cheap, but the SUB-9/ Sub-2000 have been great. The PLR/ SU16 also great. Too many birthing problems with new models, sure, but once they get production worked out, it's good to go  for the most part.

Mostly though, it's just insane to me that AUG's and Tavors cost so much. There's also always some argument about recipricating or not for charging handles. Whatever!

Oh, and the trigger is great, but reset sucks. It's much lighter than my ARX Beretta for example, but reset is some nebulous point rather than a crisp return feel.

Love mine, suppresses very well, no hearing protection required. ARs hurt the ears

That’s odd, my reset feels almost like a Glock. However, I only have 250 rounds through it at the moment. Maybe it will get mushy later.

How much does one need to spend to get an X95 to a nice 4.5 pound to 5 pound smooth trigger pull?   Are there alternative options to the $300 geiselle drop in trigger packs that are basically as good?

VFG for sure. I liked the grip-pod on mine.

I agree. Get the other bullpups if hate shooting suppressed.

Keltec makes sub quality firearms. Glad yours works but they will never be serious firearm manufacturer and shows your lack of knowledge by even comparing to steyr, a true milspec supllier.

I’ve been shooting AUGs since 1988/1989, when US Customs adopted them. Before most ever heard of them.

I am talking about a gun for home defense and shooting at the range, not a SHTF military rifle

It's really hard to beat an X95. The factory rubber buttpad sucks. I pinned and welded a muzzle device so I could put the Israeli buttpad on. Huge difference.

Since when is reliability not required for home defense?

I did the same and then bought a 18” barrel with bayonet lug too. The flat butt plate is a nice improvement.

Until today's post about a twisted bolt, I hadn't heard of any problems since the initial (2015?) teething issues with a pin that would walk out of the bolt and some rail screws that needed loctite. I've read of plenty of people who have 4K-5K through theirs without issue (a lot of that suppressed). But the design is SO simple, that it looks like it would be reliable to me (as a guy who has often taken guns down to each individual part, I like simple--it's why I like Glocks even though the ergos suck for me).

I think Keltec seems to get reliability FROM simplicity with the PLR-16, SU-16, and SUB-2000 (from what I've read/heard--I've owned NONE of them).

I DO DOUBT the RDB will have the longevity of an AUG or X95 (and it's definitely not as tough--though I've heard mixed results of torture tests with the X95).

The fact that you're admitting that the other two are better for real world adverse conditions is in itself admission that you recognize the other two are far more reliable.

And I am willing to bet that I have and older model. Serial is Z18-- -.
So far I am the only one that I have heard of having that problem.
I still really like the rifle, and as a Lefty see very few other options.

What readily available bullpup in the US isn’t lefty friendly? Both tavors have left handed bolts available and you can swap charging handles and selector both also have brass deflectors for impromptu weak side shooting. All augs sans the NATO stocked ones also have left handed bolts available. The RFB Kel Tecs other pup is forward eject. The ps90 is downward eject and the fs2000 which hasn’t been imported for awhile is forward eject. So the vast majority of options are lefty friendly. Even the Uber rare Famas  can switch ejection sides. I think the only ones that couldn’t are the crappy century ak ones.

Really it's just that they don't have the same established reputation, not that they have a reputation for being unreliable. Even then, I'm not sure why the Tavor has such a reputation given it's very limited numbers. AUG's have been around for eternity and are generally great reputation. I've only shot a USR, but it was fine.

Main problem is cost. I'd have loved to buy a FS2000 if they weren't so expensive. Folks comparing the RDB dismissively while nearly all the other bullpups are DOUBLE the price, and the main problem with RDB's is that Keltec makes cheap guns that so many people buy you can't find them in stores...

The tavor is the most numerous bullpup in the US 25k in the first year. The AUG is a rarer critter. I’m not sure if the total of all variants of the AUG in the us even equals the number of tavor SARs sold in the first year it was available on the us market. Not trying to start a pissing match as I like both but saying it’s numbers are small is not factually accurate when compared to the other available bullpups.

Technically that just means neither is numerous since I didn't say bullpup, but my point was just that the RDB doesn't have a reputation for being bad. Tavor's were popular before they even released, I'm pretty sure. Keltec just has one foot on the banana peel as soon as they launch a new firearm, even though most of their guns have been good.

Tavor's are good, AUG's are good (though I saw a bad review of some new retro one?), I think even that ugly Bushmaster thing (17S?) worked fine.

Advantage of the RDB, downward eject makes it fully ambi without modifications and adjustable gas system without an ejection port at your ear is supposed to make it great for suppressing.
And of course, it's half the price.

Advantage of all the others: They're not made by keltec. :)

So true on all being minescule for total market share. The AR absolutely destroys everything else in market share.

I actually like Kelgram’s designs I don’t trust Kel tecs follow through though. Once bitten twice shy and all. I think I’ve brought it up before but if ruger or someone else came up with a rdb clone where the gas assembly could go on any standard AR barrel, it used any ar pistol grip and had a dust cover AR style over the ejection port and was free floated I’d be pretty interested. As is I’d argue for a casual fun gun the rdb is a market leader for bullpups given its price and most get good reviews. But I can’t get over the Kel tec factor to personally purchase one.

Happy bullpup owner(Tavor, AUG, K&M)and love them all.

My offer stands: if you're in NW Houston and want to shoot my K&M up to 200 yds on a Tuesday morning pm me.

I do use a grip pod myself but I've never been in a firefight with anything so none of my crap is tested, really!

Looks are extremely subjective, and shouldn't matter, especially in a tool.
High demand and low supply would mean astronomic prices, but they aren't.
Downward ejection isn't an issue. The p90 has had adoptions.

The elephant in the room is that Keltec has big problems with build quality and reliability.
Yes, yours might work perfectly, but on a larger sample size they have a disproportionately large amount of problems.

A good warranty is generally a positive, but it also means that they've amortized your average repair costs upfront.
A good warranty is also no replacement for quality and reliability. If I have it sitting in my lap broken in the field when I need to depend on it, it doesn't matter that I can send it in to get repaired for free.

LOL  Recent Keltec folly:
Co-worker:  I think I want to get a Keltec Sub-2000.
Me:  I to have been Keltec curious.  But don't.  Resist at all cost.
Co-worker:  Yea, I'm getting a Keltec Sub-2000.
Me: It's your money.  Knock yourself out.

The next week he shows it to me.  It's pretty impressive compared to the one I got 15 years ago.  I try to be open-minded (as my wife tells me to be) that maybe Keltec has turned the corner and improving their game.

The week after that:  Recall on Sub-2000 barrels.  
Some things will never change.

I had one of the Sub2k's, wanted something that took a beretta magazine. I shot it, no problems, but I just didn't care for the metal tube and didn't want to put more money into it. Sold it to someone on this board.

Keltec's had issues here or there with production, but this is the first actual recall they've had afaik.

Likewise not trying to defer to one over the other. Just adding to Kali's points:
While the AUG may have "been around for an eternity", the Tavor is no less proven. In terms of actual rounds fired in real combat, an argument can probably be made for the Tavor to have seen more action than the AUG. Considering Israel's almost constant state of war, compared with most of Western Europe's passive position towards combat. In fact, I would even guess that the most battle tested AUG isn't even the one made by Steyr, but the one licensed to an Australian gun maker that supplies the Australian military. I've seen a lot more Australians in combat, than I have seen Austrians.

There is also IWI/IMI's reputation for rugged, durable, dependable firearms. Not that Steyr has a lesser reputation, just that I disagree with any argument that implies (intentionally or not) they somehow have a better one.
Age of the specific platform itself is also an invalid argument. Is this an argument based on the most current iterations? The age difference between most current iterations of the AUG and Tavor are negligible. AUG M1 became available in '14, the same year that the IDF decided to begin transitioning toward the X95 as their primary issue rifle. If the age of the name and base concept were the determining factor, then wouldn't that make an M-1a/M-14 with bullpup kits, the more proven weapon?

EDIT: What's worse, is that the comparison of AUG vs Tavor is distracting from the original topic. So, can we please get back to degrading ....err, debating the RDB?

Keltec shit is shitty junk

That is unless you're a Florida Community Patrol type of person !

A simple, thin piece of bent metal is the receiver/cheekpiece.  Not the populated barrel.  Not the FCG/mag well assembly.  I think KT got away with this because the buttstock attaches to the cheek piece and doesn't even touch the lower assembly (the ATF often says that the part opposing the recoil spring is the 'receiver,' which is indeed the top cover on the RDB).  Oddly, the serial is the *only* marking on the receiver part, and manf info is molded on the lower.

What the aftermarket needs from Kel Tec in order to offer support is;
-Barrel components, especially barrel extensions (so conversions can start being made; very hard to get going when the extension is proprietary)
-Bolt heads.  The RDB has a bolt head that is scaled somewhere between an AR15 and AR10 size, which frankly makes it ideal for testing out all sorts of AR-magwell compatible chamberings
-Lower small parts would also be nice for more easily/quickly populating alternate lower housings

The design is really quite minimalist from a modularity standpoint; from a functional standpoint the barrel is the chassis to which everything is fastened.  The crosspins through the barrel extension and rear sight rail rise secure the receiver/ top cover, the lower housing hangs off the same two pins as well as a pin through the end of the receiver.  Hand guard hangs from pins through the two sight rail mounts.  The BCG/recoil assembly is basically self contained, as is the lower/FCG housing, as is the barrel/gas system.  The receiver & handguard are simple parts that just close out openings.  Very simple to swap out a complete barrel assembly provided the case head is the same size, and I think it'd even be possible to extend the length of travel for longer cartridges using a slightly longer recoil rod and upper receiver.

Said it before.

Kel-Tec needs to sell the design to someone (Ruger always pops up) who can and will make sure the QC and quantities hit the shelves.

If you could also free float the barrel you might have one hell of a bull pup .

Still will probably end up buying one to suppress and hunt with.

Sure that'd help, but just look at the Remington 700; perhaps the biggest aftermarket of any bolt gun variant, despite being arguably among the least impressive from the factory in its market segment (which obviously used to mean a whole lot more decades ago than it does now, but is still valid).  It's proliferation was largely due to the fact that Remington made cheaper (but still good for a long while) bolt guns than the alternatives.

Personally, I think bullpups are inherently more compatible with European makers than American, so I'd nominate CZ to produce a better RDB ;)

Back on topic, I suppose the real question is what should the aftermarket be tackling first.  The gun is in such high demand since Kel Tec has rather impressively addressed most of the previous knocks against bullpups (side ejection, poor triggers, gas venting), apart from simply wanting a slightly *nicer* gun with an attendant higher price that competes more directly with the other bullpups, what still needs fixing?

Ruger as a model for QC?  Ever hear of the early SR-762s?

Depending on the numbers that could be sold and whether the investment would be recouped, I would offer an alternative lower receiver since the part with the magwell and pistol grip are not serialized.  The design would offer the ability to use AR grips (since that seems to be the biggest whine point on just about every new gun..."Does it use AR grips?"  Almost as annoying as "Does it use Glock mags?") and I would somehow modify the magazine release to be somewhat more protected than out in the open as it is now.  In a perfect world, I would explore whether the lower could be fabricated from aluminum instead of polymer.

But the deciding factor would be demand and the number of units that could be sold at a price that people would actually buy.

It could be, if they could prove to have good consistent QC.

But they can't or won't, so it's moot.

I really want to like this rifle but can't get past the random serious issues that they appear to have that makes me lose faith in it operating well.

1) I don't have any issue with the plastic, and I havn't heard of anyone having any issues with their plastic.
2) I can see the issue with downward ejection. While I also don't care about ambidextrous shouldering. But I havn't heard of anyone having issues with the opening at the bottom, in terms of debris getting in. The only time I've seen it become an issue is with In-Range's ridiculous extreme dunk in mud test.
3) I think the RDB looks cool. It's like the DMR from HALO.

Anyhow, Keltec justifiably has a reputation for putting out poor quality products, but they seemingly managed to put out a good product with the RDB. From day 1 of its release, there has been a large consensus that the RDB has met as well as exceeded expectations for quality and reliability. You can't always assume a manufacturer is going to produce all their products with a uniform degree of quality and attention. They make some products better than others, and Keltec has made the RDB better than any of their previous products. Keltec has found their golden child. Most people who own them have little or no issues, and some with many thousands of rounds fired.  While there have been a few known issues that have risen, they have been quickly resolved by Keltec. While I really adore my RDB, I admit that I am leery about trusting it in a SHTF situation, even though many reviewers have stated that they would. It still has a while to go to solidify its reputation. But if it does so, I can see the RDB proving capable as a SHTF rifle, or even entering LE or even military issue one day.  I would just like to see the rifle thoroughly tested. Something like Hank Strange's low-crawl shooting mud test that he did with the Tavor several years ago.