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Odin has a 1 in 9 twist barrel that was leftover from the pre-production guntoober marketing blitz. His exact results and possibly even the trends are unlikely to carry over to the production 1 in 7 twist barrels. Alas, if it were only that easy. Hopefully, the heavier bullets do better in the 1 in 7 (which was why KT made the change, everyone online was complaining about 1 in 9).
That makes total sense. So, I guess its round hunting for me to find the round my rifle likes.
 

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Discussion Starter · #42 ·
Yes, do you have cost figures? How much did this foreend grip cost you? How long did it take you to manufacture it?

Are you making it to sell? If so, how much?

They look so cool that I am getting very tempted although I really like the stock handguard.
The handguard won't fit without some serious modifications to the polymer lower. I would not recommend doing what I am doing unless you're okay with potentially ruining the rifle. I don't know how losing the front takedown pin will effect the long term integrity of the lower.

One of my goals was to show that KT could have easily gone free-float handguard from the factory if that wanted to. Considering that all I had to do was to put an extension on the receiver and change the front of the polymer lower just a little to let the extensions protrude, those are easily things KT could have put in the design back in 2013. The only "hard" thing would be to design a QD system for takedown.

i mean, they could have just made the polymer lower longer to have an integrated handguard. I suspect they were limited by their injection mold machine.
 

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The handguard won't fit without some serious modifications to the polymer lower. I would not recommend doing what I am doing unless you're okay with potentially ruining the rifle. I don't know how losing the front takedown pin will effect the long term integrity of the lower.

One of my goals was to show that KT could have easily gone free-float handguard from the factory if that wanted to. Considering that all I had to do was to put an extension on the receiver and change the front of the polymer lower just a little to let the extensions protrude, those are easily things KT could have put in the design back in 2013. The only "hard" thing would be to design a QD system for takedown.

i mean, they could have just made the polymer lower longer to have an integrated handguard. I suspect they were limited by their injection mold machine.
Is KT aware of your modifications? Maybe they'll make an updated RDB with your modifications. Extending the polymer lower does not seems like a terribly difficult thing to do.
 

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Discussion Starter · #44 ·
Is KT aware of your modifications? Maybe they'll make an updated RDB with your modifications. Extending the polymer lower does not seems like a terribly difficult thing to do.
It's actually relatively hard. Injection molding plastics is kind of like witchcraft. The molds are obscenely expensive and take a lot of tuning and tweaking. irtv's wwsd project has a good look at how you would go about making a polymer lower.
 

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You may not be interested in any SHTF or zombie situation, but I am. That is my primary purpose for this rifle.

And once again, you could not conceive of a situation that you might need to shoot a zombie at 200yds. My goodness, either you lack any tactical sense or you are simply baiting me. Since, I don't believe you are totally tactically clueless, I'll assume that you are simply baiting me so I'll disengage and not allow myself to be drawn into a long fruitless discussion.

Well, considering zombies aren't real, I don't really give much thought to the tactics needed to dispatch one. But I did answer your question with tactics that would be appropriate if they did exist. They also apply in a SHTF scenario where you don't want to give your position away. If you want to discuss further, feel free to start a new thread in The Counter sub-forum.
 

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The handguard won't fit without some serious modifications to the polymer lower. I would not recommend doing what I am doing unless you're okay with potentially ruining the rifle. I don't know how losing the front takedown pin will effect the long term integrity of the lower.

One of my goals was to show that KT could have easily gone free-float handguard from the factory if that wanted to. Considering that all I had to do was to put an extension on the receiver and change the front of the polymer lower just a little to let the extensions protrude, those are easily things KT could have put in the design back in 2013. The only "hard" thing would be to design a QD system for takedown.

i mean, they could have just made the polymer lower longer to have an integrated handguard. I suspect they were limited by their injection mold machine.
The piston is attached to the barrel, so it's never going to be a true free float system. Using the LI handguard with a bipod or rest positioned towards the rear can improve accuracy.
 

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Discussion Starter · #47 ·
The piston is attached to the barrel, so it's never going to be a true free float system. Using the LI handguard with a bipod or rest positioned towards the rear can improve accuracy.
And the AR gas tube is attached to the AR barrel so it'll never be free floated either. But removing the handguard's influence on the barrel means you don't get vertical stringing from deflection due to handguard pressure. As I've written in the OP, I believe there is no rationale for not having a free floated HANDGUARD. The LI handguards clearly show there is room for improvement, so why not build them that way from the start?

My entire premise is that the RDB has glaring design oversights. You disagree. Cool.

Also, does the LI rail eliminate hanguard deflection if you put the bipod or rest at the end? Does the LI rail improve "accuracy" (precision) over just removing the handguard? I haven't seen reports of people testing the RDB without a handguard in place but I could have missed those posts.
I know the Li rail can be a hassle to install and swap back and forth, so I imagine there aren't a ton of A/B tests.
 

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Well, considering zombies aren't real, I don't really give much thought to the tactics needed to dispatch one. But I did answer your question with tactics that would be appropriate if they did exist. They also apply in a SHTF scenario where you don't want to give your position away. If you want to discuss further, feel free to start a new thread in The Counter sub-forum.
Of course zombies aren't real - zombies in the sense that they are dead or undead. But zombie-like is quite real and possible.

I'm sure you are familiar with rabies and how it makes the victim rabid, mad and crazy. Our saving grace has been that rabies is not very contagious, so it hasn't been able to take hold in numbers that are of concern. Now enter COVID which is very contagious. An evil dictator (China) is already planning or even making a genetically engineered COVID shell with a Rabies-like internal. Imagine a virus that is as rabid as Rabies and as contagious as COVID. You will have a hoard of zombie-like rabid people in no time. You still think I'm nuts for planning for a zombie-like SHTF scenario? Far from being unlikely, I submit to you that it is the most likely SHTF scenario.

If COVID has taught us anything, is that it is relatively easy to genetically engineer a virus that is designed to be highly infectious. COVID is just the shell carrier that is highly contagious. The more lethal and dangerous part is the rabies-like virus payload inside.

You still can't think of a situation where you might need to make that 200yd head shot? Just imagine a hoard of rabies-infected zombie-like people running towards you. I'm sure you are NOT going to try to make that 200yd head shot but wait for them to come closer since your SHTF rifle is "not designed to be a precision rifle", and "you don't want to give your position away".

Some posters here are dumping on me for seeking a more accurate RDB, but I think they are just not thinking tactically and realizing the threat that is imminent.

With apologies to Anach for hijacking this thread, but I hope this is the last reply I have to make on the zombie SHTF scenario.
 

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And the AR gas tube is attached to the AR barrel so it'll never be free floated either. But removing the handguard's influence on the barrel means you don't get vertical stringing from deflection due to handguard pressure. As I've written in the OP, I believe there is no rationale for not having a free floated HANDGUARD. The LI handguards clearly show there is room for improvement, so why not build them that way from the start?

My entire premise is that the RDB has glaring design oversights. You disagree. Cool.

Also, does the LI rail eliminate hanguard deflection if you put the bipod or rest at the end? Does the LI rail improve "accuracy" (precision) over just removing the handguard? I haven't seen reports of people testing the RDB without a handguard in place but I could have missed those posts.
I know the Li rail can be a hassle to install and swap back and forth, so I imagine there aren't a ton of A/B tests.
The gas tube on a DI AR is thin and flexible, and presents very little in the way of deflection or interference when it comes to barrel harmonics. Piston ARs tend to be less accurate than their DI counterparts. Not always, but most of the time. I prefer piston guns because it means I don't have to clean them as much. Less cleanin' means more shootin'...

Yes, the LI handguard improves accuracy over the stock polymer one when using a bipod or rest at the end - to a small degree. Being aluminum, it doesn't flex the same way the polymer handguard does. I would imagine the aluminum handguard from Kel Tec would also improve accuracy, but I haven't tried one. I don't think making the handguard a part of the chassis would do much better.

Remember, the RDB isn't Kel Tec's first bullpup rodeo. They took what they learned from the RFB and built the RDB around the 5.56 cartridge. If George Kellgren wanted to design a bullpup capable of sub-2 MOA accuracy, he probably would have.
 

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Discussion Starter · #50 ·
The gas tube on a DI AR is thin and flexible, and presents very little in the way of deflection or interference when it comes to barrel harmonics.

Yes, the LI handguard improves accuracy over the stock polymer one when using a bipod or rest at the end - to a small degree. Being aluminum, it doesn't flex the same way the polymer handguard does. I would imagine the aluminum handguard from Kel Tec would also improve accuracy, but I haven't tried one. I don't think making the handguard a part of the chassis would do much better.
The KT defender rail is mounted in the exact same way the normal handguard is so it rattles around and certainly doesn't help with barrel assembly rigidity. The reason the RDB has handguard deflection is that it is affixed in only 2 locations with pivots, and one of those places is the gas block so the entire thing is a class 3 lever. The LI rail is still mounted to the gas block, but also has those special mounting bracket thingies to try and stiffen up the connection. Alternatively, you could go to a free floated handguard and not have to deal with mounting anything to the gas block or have any handguard pressure deflection.

The barrel harmonics are the barrel harmonics. Let the barrel whip, it's physics. What matters is that it's repeatable. Having minute variations in force at the front of the barrel is going to cause the barrel to behave differently with every shot.
 

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The KT defender rail is mounted in the exact same way the normal handguard is so it rattles around and certainly doesn't help with barrel assembly rigidity. The reason the RDB has handguard deflection is that it is affixed in only 2 locations with pivots, and one of those places is the gas block so the entire thing is a class 3 lever. The LI rail is still mounted to the gas block, but also has those special mounting bracket thingies to try and stiffen up the connection. Alternatively, you could go to a free floated handguard and not have to deal with mounting anything to the gas block or have any handguard pressure deflection.

The barrel harmonics are the barrel harmonics. Let the barrel whip, it's physics. What matters is that it's repeatable. Having minute variations in force at the front of the barrel is going to cause the barrel to behave differently with every shot.
So uh..Any updates?
 

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Very nice, I'm curious what the AUG looks like with a Shorty sitting on top.

The groups you have posted in the imgur album reminds me the groups I got with my RDB-C, I was using a RDS with 3X magnifier as well. I did my reporting on the range visit at the beginning of this pandemic so I have very limited ammo selection. But I did find the rifle likes Hornady Frontier 75 gr BTHP over the Federal AE XM195 55gr FMJ. Link here

Well, what can I say, the RDB is after all a budget bullpup fits where it needs to be in the market. I'm happy to have acquired it for a good price and it makes me happy to see it delivers on my expectations.
 

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Discussion Starter · #56 · (Edited)
The groups you have posted in the imgur album reminds me the groups I got with my RDB-C, I was using a RDS with 3X magnifier as well. I did my reporting on the range visit at the beginning of this pandemic so I have very limited ammo selection. But I did find the rifle likes Hornady Frontier 75 gr BTHP over the Federal AE XM195 55gr FMJ. Link here

Well, what can I say, the RDB is after all a budget bullpup fits where it needs to be in the market. I'm happy to have acquired it for a good price and it makes me happy to see it delivers on my expectations.
I hadn't seen your thread before, must have missed it. I was a little surprised the 77gr HPBT didn't do better for me considering the reports by others.
If I get a chance next week, I might try shooting some 20rd groups from a sled to see if the horizontal spread tightens up. No point in hoarding the 77gr stuff when 55gr HPM delivers equal results (my RDB used to hate this stuff, so maybe an improvement?)
I also have some 55gr IMI I can try. The results for 5.56 m193 were promising, maybe they can tighten up a bit.

Very nice, I'm curious what the AUG looks like with a Shorty sitting on top.
I'll try to get a photo at some point, I only have pictures of it wearing a eotech and D-EVO.
 

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Range report and precision analysis
View attachment 57001

Took the "RDB" to the range today along with the AUG and 100 rounds of select ammo:
  • Hornady Frontier 55gr m13 (bulk 1000rd bag)
  • Hornady Frontier 55gr .223 HP Match (bulk 150rd box)
  • PMC Bronze 55gr .223 FMJ (stripper clip bandolier, no annealing, no sealed primer)
  • Winchester 64gr Deer Season XP (every round is crimped and seated differently, case mouths are often trimmed at an angle, I mistakenly identify it as 65gr in analysis)
  • Sellier & Bellot 77gr NATO HPBT "Tactical"
I pre-registered the analysis (which is how you do good science) and shot according to the following schedule:

The deviations and experimental addendums are:
  • I fired 5 rounds of PMC bronze in each rifle to confirm or adjust zero.
  • I jacked up 2 rounds of Hornady Frontier HPM in the AUG (first malfunction) and fired a total of 8 rounds and analyzed all 8 without a flier allowance.
  • On a few AUG strings, I shot 6 rounds instead of 5. I reduced the second string to 4 rounds as required.
  • AUG was shot using a March 1-10 Shorty on ~9.5x
  • Fired strings at a cadence of ~3 seconds/round
  • Tested all rounds for each type of ammunition before moving to the next (RDB first)
This imgur album has the raw targets and the targets with analysis using OnTarget TDS. Fliers were manually excluded from analysis.
Rifle
Ammo
CTC
MOA
X
Y
Off X
Off Y
RDB​
3.425​
3.271​
2.855​
2.385​
-0.981​
-0.592​
RDB​
4.103​
3.918​
3.275​
3.916​
-1.613​
0.607​
RDB​
3.149​
3.008​
3.064​
2.251​
-0.234​
0.522​
RDB​
2.588​
2.572​
2.299​
2.054​
-1.285​
2.088​
RDB​
2.092​
1.998​
1.756​
1.757​
0.414​
0.469​
AUG​
2.747​
2.624​
1.289​
2.747​
-2.733​
0.479​
AUG​
2.762​
2.638​
1.325​
2.744​
-0.745​
-1.561​
AUG​
2.735​
2.612​
1.554​
2.345​
-0.075​
-0.303​
AUG​
2.573​
2.458​
1.53​
2.537​
-2.223​
1.606​
AUG​
1.821​
1.739​
1.76​
1.664​
-1.35​
0.475​

Shockingly (or not), the Winchester Deer Season stuff, despite looking like this, shot the tightest groups.
I intentionally did not post the order I shot the rounds in. The analysis order is randomized as well. Shooter fatigue is going to play some role but I do not have the dataset to really test for covariance/confounding variation. I'd be interested in guesses as to the order I shot them in.

Just a reminder, I am not a very good shot and my eyes are pretty bad. The magnifier really helped being able to center the dot on the target. The quality of shooting is consistent with my typical performance regarding breathing control and trigger press. I tried to keep a consistent cadence and that undoubtedly added some variation (I didn't spend 1 minute making each shot perfect). I also don't have a solid control group for the RDB. I never did a thorough analysis of spread but historically I got anywhere from 2 to a lot of MOA. Remember, the variability was one of the frustrations I had with this particular specimen.
I think a beneficial approach is to look at the performance of the RDB vs the AUG for a given ammunition type in terms of percent difference. The AUG was surprisingly consistent across all ammunition and provides a decent baseline for showing minimum ammunition performance with this particular platform (shooter, 1 in 9 AUG, weather conditions).

An interesting data trend is that the vertical spread for the AUG is typically what sets the max center-to-center where as the horizontal spread seems to be the primary driver of max center to center for the RDB. The primary exception is the Winchester 64gr which has very even x/y spreads for both weapon platforms. When the x/y spread is so different, I would typically look for an external source of variation (shooter, barrel deflection from handguard, etc).

I'm sure the use of a 10x optic is going to come up. I probably should have shot the AUG at 3x, but I wanted good data for the AUG for other purposes. If nothing else, I have an ammunition ladder that others can test and use to guide their purchases.

I am not sure the modifications have increased precision. What they have done is enable to me rest the handguard on support and not worry about deflection. Physics would suggest that would also influence precision in some way, but without a control group, it's hard to draw reliable conclusions. Zero retention needs a few more range trips to test, but I have (unfounded) high hopes.

[I didn't blow myself up, YAY!]
Eh I wouldnt worry about using the 10x on the Aug.. I started my MDR vs RDB comparison that way (after RFB vs MDR) and well..The higher mangification just let you see that target better..It doesn't change the groups you were gonna get.

Cool Stuff..Now if I can remember how to put that into a bubble chart like I did for the RDB Ill post it here for ya.

PMC Bronze is the Zero ammo correct?
 

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Discussion Starter · #58 · (Edited)
PMC Bronze is the Zero ammo correct?
For better or worse, yes. The offset x/y values are based on POA/initial PMC Zero.

Cool Stuff..Now if I can remember how to put that into a bubble chart like I did for the RDB Ill post it here for ya.
Thanks. If you can't remember how to do the chart, I can probably figure it out. It probably uses bubble charts.

Eh I wouldnt worry about using the 10x on the Aug.. I started my MDR vs RDb comparison that way (alter RFB vs MDR) and well..The higher mangification just let you see that target better..It doesn't change the groups you were gonna get.
Unless, of course, you have trouble seeing the target without magnification. I don't think the magnifier was too much of a hindrance. If anything, the extra magnification may have led me to taking half assed shots that looked "good enough"
 

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For better or worse, yes. The offset x/y values are based on POA/initial PMC Zero.


Thanks. If you can't remember how to do the chart, I can probably figure it out. It probably uses bubble charts.


Unless, of course, you have trouble seeing the target without magnification. I don't think the magnifier was too much of a hindrance. If anything, the extra magnification may have led me to taking half assed shots that looked "good enough"
Modified RDB results.
Below just represents the accuracy, group size and offset (should you shoot at the same target).

Average group for the above is 2.93moa for all shots fired.


Average group size for the above is 2.4moa
 

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Discussion Starter · #60 ·
Modified RDB results.
Below just represents the accuracy, group size and offset (should you shoot at the same target).

Average group for the above is 2.93moa for all shots fired.


Average group size for the above is 2.4moa
Thanks for making those. The bubble scale seems slightly funky, like on the m193 55gr hornady frontier.

I was at the range last Wed and did a few more tests:


Slightly worse shooting that day, but it was also "can't feel your fingers cold"


Rifle
Ammo
CTC
MOA
X
Y
Off X
Off Y
AUG​
IMI 55gr M193​
3.628​
3.466​
3.299​
3.215​
0.605​
-1.652​
AUG​
Winchester_64gr_deer season XP​
1.847​
1.764​
1.129​
1.653​
-1.268​
0.834​
AUG​
ADI 69gr SMK​
2.043​
1.951​
1.127​
1.76​
-1.914​
-1.708​
RDB​
IMI 55gr M193​
4.272​
4.081​
3.054​
3.597​
-0.248​
0.378​
RDB​
Winchester_64gr_deer season XP​
2.674​
2.554​
2.32​
1.855​
0.433​
0.496​
RDB​
ADI 69gr SMK​
3.155​
3.013​
3.099​
1.492​
-0.657​
1.774​

Still the same conclusion: I certainly didn't make it worse, but not sure I made it better, apart from the handguard pressure induced stringing.

Still sucks the $1.30 a round ammo is the best shooting, despite looking like factory rejects.
 
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