The difference in ballistics between a 16 and 17 inch barrel isn't that great. Typically, a pencil barrel would be inherently less accurate because of greater barrel whip, although developing a custom load specific to the rifle can remedy a lot of that problem. However, the barrels are not free floated on these bull pups so they aren't 500+ yard precision rifles and the differences in accuracy probably aren't all that that much between the four models, although the RDB Survival seems optimized for fairly short range shooting using iron sights. It's capable of better accuracy than that but the design lends itself to simple and lightweight off hand shooting rather than scoped bench rest shooting.

Compared to precision bolt action rifles, all of the RDB variants have a pencil barrel. The more pencil barrel versions of the RDB will probably be 2 MOA capable, or better. The less pencil barrel RDBs will probably be 1 to 1.5 MOA. The lighter barrels will heat more quickly, resulting in faster change to the point of impact, but once the barrel is at a fairly constant elevated temperature, the new POI will stabilize. The slightly heavier barrel RDBs will have a slower POI drift over the first several rounds.

I think the four RDB versions are more a matter of use preference rather than there being major differences in their capabilities.

 

Thank you so much for the detailed reply! So it is indeed a matter of preference (and cost). Thanks for the sanity check, I'm actually coming around to the look of the RDB17, particularly in green as it gives off major Halo vibes. Gotta look cool when you're defending the homestead, otherwise what's the point?!

Jokes aside, you've helped simplify the process for me and I appreciate it. Thanks again

 

The RDB Defender doesn’t have a pencil barrel. That was the plan initially but it’s more of a thin to medium contour. It also doesn’t have the lighter bolt carrier op-rod like the Survival has. It is 26” long (without the muzzle device), same as the Survival, but you can collapse the butt-stock to get it to around 24.75” long. The length specs are all the same as the Survival (minus the flash hider at the end).

In my opinion there is no reason to buy the original RDB when the Defender is available. Shorter, lighter, adjustable stock, better forend. Plus the desert tan or OD green looks awesome with the aluminum matching handguard.

 

In my opinion there is no reason to buy the original RDB when the Defender is available.

Collect the whole set!

I think I watched too many Saturday morning cartoons, where cheap plastic toys were used to coerce kids into getting their moms to buy a lot of breakfast cereal that was over 50% sugar.

 

I must be living in a cave. I had to see what the Defender was. For me I think I'd like it more than the 17" that I own, except for the aluminum fore end. Why? I live a very cold climate and aluminum, even when wearing gloves, sucks the heat out of anything it touches. Plastic not so much. I like the adjustable stock that it has. But the weight diff' would be unnoticeable to me. If I was buying new I'd buy the Defender and figure out a way to insulate my hand from the aluminum. Maybe with a Grove Tec wrap? Of course something similar could be made out of a dollar store potholder and gaffer or camo tape. Directions on youtube.

Rail Wrap 6" - MultiCam® - GTAC331

MULTI-FUNCTIONAL HEAT GUARD, M-LOK®, SLING STORAGE, CABLE MGMT- Designed to Wrap Around a Handguard or Non AR Forearms- Mitigate Heat Transfer (Not for Use on Suppressors)- Integrated Elastic Webbing for Sling Storage- M-Lok® Compatible For Bottom & Top Mounted Accessories- Organize Electronic...

grovtec.com

 

The RDB Defender doesn’t have a pencil barrel. That was the plan initially but it’s more of a thin to medium contour. It also doesn’t have the lighter bolt carrier op-rod like the Survival has. It is 26” long (without the muzzle device), same as the Survival, but you can collapse the butt-stock to get it to around 24.75” long. The length specs are all the same as the Survival (minus the flash hider at the end).

In my opinion there is no reason to buy the original RDB when the Defender is available. Shorter, lighter, adjustable stock, better forend. Plus the desert tan or OD green looks awesome with the aluminum matching handguard.

Eh..With the LuckyIrishman handgaurd the Original Rdb17 is the same weight as the Defender with a but with a slightly longer barrel.
The Extendable stock is a "meh" for most folks, just like it is on the Hellion.Well..unless you have really long arms.

 

Sure, I’m not saying you can’t spend $200 bucks to buy a new handguard for the basic RDB, nor am I saying that the adjustable buttstock is perfect, but I’d still rather it come from the factory with those items than not have them or have to pay additional money.

 

Personally, I kind of wish they offered the RDB-S with a pistol grip option.

The only reason for the adjustable stock is to avoid the NFA.

Interestingly, I recently learned the reason for the adjustable stock on the Hellion is to push the brass further away from your face when shooting offhand. It's not so much for gorilla arms.

 

I have the RDB 17. I love it.
I tend to use my guns as they come, with minimum modifications. I'll upgrade plastic for metal internals, ect... But otherwise, KISS.
I cannot see any advantage to the Defender over the RDB17. Someone below noted some advantages and disadvantages to the aluminum fore end. The plastic of the RDB certainly will not transmit heat as rapidly. And in my subjective opinion, will get less slippery in wet or sweat conditions. I've not used an aluminum fore end on anything. But I never find my RDB slippery.
Overall though, I would never trade off a heavy barrel for a pencil barrel just to save 5.8 oz. and no practical reduction in length, for a rifle. 6 ounces is worth consideration on a handgun. But on a rifle, not so much...in my opinion.
A pencil barrel is going to be less stable when you put a lot of rounds through it in a short time. I don't see how it can be avoided. But as somebody below noted, you might learn to compensate for that. For a fun gun, that you have the time and patience to pace the number of rounds and time frame, I'm sure it's fine, especially if you learn its nuances.
I have my RDB17 and an SU16c, both have heavy (for 5.56mm) barrels. I had truck/pack gun and SHTF use in mind when choosing them. So for me, the choice would be simple.
The great thing is that Kel Tec makes these different models because we all have our preferences and uses. I love every Kel Tec I have. Whatever you decide on, I'm sure you'll like it.

 

Get a 17, Forget the collapsible but stock idea, its a fail.
Then buy a C "Hunter" forearm from KT. Put it on. Done.
Or you can put on a Survival or Defender Forearm if you want short.

Then go the next step and swap the charge lever for a Defender lever.
Get safety levers from Dan Gaga Designs and the slide release lever from Lucky Irishman.
Make index scribes on the top rail screws and watch for rotation.
Get an extra 404 buffer from KT to put in the rear to keep the action rod in place.
Get extra firing pins and make sure they all work.

 

Excellent!
Now that's some definitive help.
Thanks.

 

I don't see much value in the measures KT designed into the S and D for getting more compact. I can see the pencil barrel being an advantage for the backpacker. I suspect very few people will choose an RDB for trekking. Being able to shave an inch off the back isn't worth the the extra screws needed to keep it on. I suspect more shooters just use it collapsed. I would rather not have a moving stock that gives only an inch of lenght.

As for the 16 vs 17 inch option, I can say because I did it, a C forearm on a 17 is absolutely transforming. KT absolutely missed the mark not offering the 17 with that stock. You just have to try it. The C forearm will NOT work on a 16". It will bolt up, but will be too long.

I just think the 17 is the better RDB to start with but the forearm is Waaay to fat and ugly. It does have sling eyelets which is something I had to add to my C stock.

I should also say one could have good results with one of the metal forearm options from Lucky Irishman, or KT.

To answer the question, why say buy a 17 and make all the changes? Because the end result is the gun KT should have made available. Im not going to suggest someone get a model with a gimmick for a but stock and a shorter barrel when, being a bullpup, its already very short. Having to pay extra to add a C stock is a bad on KT, not on me for suggesting it and Im not going to recommend a D with features I don't need, and IMO, are a detriment.

Its all personal preference.

Hey, KT, offer that C arm on the 17.

Oh, I should probably get the Dan Haga but stock.
A vast improvement over the OE.
Tried the flared mag well but too wide and dug into my wrist. Took it off. The DH safety levers (not in this pic) are a must.
The Maggy MBUS Pros are just right.

 

Yeah I have a Hunter, I’m familiar with the C/Hunter fore end stock. Basically any of the stocks other than the original fore-end are better than the original, and on the shorter Defender and Survival barrel the Survival hand guard is similar to the Hunter, same profile just shorter.

The Defender doesn’t have a pencil barrel, its just a medium to thinner contour.

Yes, everyone just leaves the butt stock collapsed on the Survival and Defender and it gives you a butt stock just like all the others. There are no extra screws, just the standard two screws to hold the butt stock on and special metal spacers to allow it slide out if you want. But, because you CAN extend it, they can make the Defender and the Survival 24.75” long with the butt stock collapsed, and if you extend the butt stock it’s the required 26” long.