[Laserbait]

May I know where you read that?

I believe it was in one of the handguard threads here, and on the Lucky Irishman Facebook page.

 

[Jojo Jaro]

The Rdb hunter has a thicker barrel than The standard 17 model?

You could grab a RDB Hunter model and use the thicker barrel on that one if you wanted. I took mine and cut it down to 18” and with 77gr MK262 clones I can get 1-2 moa consistently. Closer to 2 moa most of the time. That to me is fantastic for a piston bullpup.

If that is the case, is the RDB Hunter free of the foreend grip pressure problem? Maybe due to its thicker barrel?

Does the RDB 20 have the Hunter's 20" thicker barrel? Does anyone here have an RDB 20?

 

[IAm_Not_Lost]

[

The Rdb hunter has a thicker barrel than The standard 17 model?

If that is the case, is the RDB Hunter free of the foreend grip pressure problem? Maybe due to its thicker barrel?

Does the RDB 20 have the Hunter's 20" thicker barrel? Does anyone here have an RDB 20?

Well, I have an RDB Survival and an RDB Hunter. The Hunter has a 0.625” barrel under the handguard - and to just forward of the gas block - and then tapers to 0.557” at the 18” mark of the barrel (I cut my 20” barrel down). The RDB Survival has a barrel thickness of 0.552” under the handguard and 0.475” just forward of the gas block and is consistent until the muzzle.

So, if someone has the regular RDB that they can measure……we can know all the barrel profile thicknesses.

And yes, I thought the 20” Hunter barrel was thicker, but now that I measure it, it is about the same as a light to medium contour AR barrel. I guess compared to the true pencil barrel of the Survival model it looks a lot bigger…..

 

[Jojo Jaro]

[



Well, I have an RDB Survival and an RDB Hunter. The Hunter has a 0.625” barrel under the handguard - and to just forward of the gas block - and then tapers to 0.557” at the 18” mark of the barrel (I cut my 20” barrel down). The RDB Survival has a barrel thickness of 0.552” under the handguard and 0.475” just forward of the gas block and is consistent until the muzzle.

So, if someone has the regular RDB that they can measure……we can know all the barrel profile thicknesses.

And yes, I thought the 20” Hunter barrel was thicker, but now that I measure it, it is about the same as a light to medium contour AR barrel. I guess compared to the true pencil barrel of the Survival model it looks a lot bigger…..

When you cut down your 20" barrel, were you able to rethread the end? Is the profile still thick enough to be able to rethread the ends to accept a 1/2"-28 suppressor?

 

[Jojo Jaro]

[



Well, I have an RDB Survival and an RDB Hunter. The Hunter has a 0.625” barrel under the handguard - and to just forward of the gas block - and then tapers to 0.557” at the 18” mark of the barrel (I cut my 20” barrel down). The RDB Survival has a barrel thickness of 0.552” under the handguard and 0.475” just forward of the gas block and is consistent until the muzzle.

So, if someone has the regular RDB that they can measure……we can know all the barrel profile thicknesses.

And yes, I thought the 20” Hunter barrel was thicker, but now that I measure it, it is about the same as a light to medium contour AR barrel. I guess compared to the true pencil barrel of the Survival model it looks a lot bigger…..

Odin, can you please measure the barrel profile of your RDB17? We can compare that with the RDB Hunter.

 

[odinforever2000]

[



Well, I have an RDB Survival and an RDB Hunter. The Hunter has a 0.625” barrel under the handguard - and to just forward of the gas block - and then tapers to 0.557” at the 18” mark of the barrel (I cut my 20” barrel down). The RDB Survival has a barrel thickness of 0.552” under the handguard and 0.475” just forward of the gas block and is consistent until the muzzle.

So, if someone has the regular RDB that they can measure……we can know all the barrel profile thicknesses.

And yes, I thought the 20” Hunter barrel was thicker, but now that I measure it, it is about the same as a light to medium contour AR barrel. I guess compared to the true pencil barrel of the Survival model it looks a lot bigger…..

Its the same under the handguard and just forward of the first tower 0.625" (under the handguard) - to just behind of the gas block (second Tower)- and then tapers to 0.561 from the front of the gasblock to just behind my muzzle device (13" to 17" inch mark).

 

[IAm_Not_Lost]

When you cut down your 20" barrel, were you able to rethread the end? Is the profile still thick enough to be able to rethread the ends to accept a 1/2"-28 suppressor?

Yes but not by much. Certain muzzle devices would work just fine. My Dead Air devices have a slightly flared base almost, so I added a shoulder ring to sit against the minimal shoulder left after cutting and threading to act as a true shoulder for the muzzle device. Just like what many people do on the Scar 17. Same basic appearance.

Its the same under the handguard and just forward of the first tower 0.625" (under the handguard) - to just behind of the gas block (second Tower)- and then tapers to 0.561 from the front of the gasblock to just behind my muzzle device (13" to 17" inch mark).

Well, looks like they’re the same and I was wrong. For some reason I thought the standard model had a barrel about the same thickness as the Survival model, thats what I picture when I think “pencil
barrel”.

With all of this said, I wouldn’t have any concern that the barrel thickness of the standard model is somehow the limiting factor with regard to accuracy. Just my thought anyways.

 

[odinforever2000]

Yes but not by much. Certain muzzle devices would work just fine. I added a shoulder ring to sit against the minimal shoulder left after cutting and threading to act as a true shoulder for the muzzle device. Just like how the Scar 17 needs. Same basic appearance.



Well, looks like they are the same, and I was wrong. For some reason I thought the standard model had a barrel about the same thickness as the Survival model.

Naw thats the Defender model with the Keltec aluminum handguard (Which is just a Survival with the standard 17 lower)
..And they only did that to save weight (and lost an inch of barrel too) that they re-added (weight) with the extendable stock...

With the standard RDB and an LI handgaurd your at to 6.7lbs (Same as the defender but with 1 inch more barrel (thicker too) and no extendable stock).

 

[gxer]

My two cents, if a thicker barrel improves the rigidity of the entire barrel assembly, then you will see less variation of POI shift due to external pressure to the barrel, which improves accuracy. In RDB you have the top rail connected to the barrel in two places rigidly (if all bolts on the rail are torqued down), essentially forming an elongated steel rectangle tube cross section, this gives barrel lower chance to flex under external pressure:

Here is another example of rigidity induced accuracy, the Walther WA2000 sniper rifle, also a bullpup, non free floating barrel but check out how rigidly the barrel sits in the frame of the rifle (credit here):

The LI rail adds even more additional rigidity to the RDB by attaching rigidly to the gas block and lower receiver making the barrel even less likely to flex under pressure.

Free floating barrel is a nice idea but I think it's really best for thin profile pencil barrels, when you apply free floating to medium and heavy barrel, the weight of the barrel itself may cause additional barrel whip during firing and impact accuracy.

 

[Laserbait]

My two cents, if a thicker barrel improves the rigidity of the entire barrel assembly, then you will see less variation of POI shift due to external pressure to the barrel, which improves accuracy. In RDB you have the top rail connected to the barrel in two places rigidly (if all bolts on the rail are torqued down), essentially forming an elongated steel rectangle tube cross section, this gives barrel lower chance to flex under external pressure:

Unfortunately steel and aluminum have different expansion characteristics under heat. Under fire/heat, if the rear screws are torqued down on the aluminum top rail, the aluminum will expand about 2x as much as the barrel steel will, and cause the barrel to bow in a downwards arc. This is the reson that KT slotted the rear rail and uses a wave washer on the screw, so that when the rail expands, it has somewhere to move without stressing the barrel. If the top rail were also made of the same steel as the barrel, then this would not be an issue.

Here is another example of rigidity induced accuracy, the Walther WA2000 sniper rifle, also a bullpup, non free floating barrel but check out how rigidly the barrel sits in the frame of the rifle (credit here):

The LI rail adds even more additional rigidity to the RDB by attaching rigidly to the gas block and lower receiver making the barrel even less likely to flex under pressure.

Free floating barrel is a nice idea but I think it's really best for thin profile pencil barrels, when you apply free floating to medium and heavy barrel, the weight of the barrel itself may cause additional barrel whip during firing and impact accuracy.

The heavier profile a barrel is, the more rigid it is and will resist whip. This is why precision shooters use heavy free floated barrels. If you look at the unlimited class railguns, you'll see barrels that are upwards to 2-3" in diameter and free floated.

 

[gxer]

The heavier profile a barrel is, the more rigid it is and will resist whip. This is why precision shooters use heavy free floated barrels. If you look at the unlimited class railguns, you'll see barrels that are upwards to 2-3" in diameter and free floated.

Fair point there. I believe the barrel profile is the key here. You have SCAR with a free floated pencil barrel that is known for its accuracy. Barrel quality and manufacture process also comes into consideration for improving accuracy, I though the heavy barrels you typically only see on bolt guns are made to negate the heat induced barrel expansion which affects accuracy.

 

[odinforever2000]

I typically shoot my Rdb (3.5x prisim, king comp and Li handgaurd) side by side my Ar15 (timney trigger and free float aero handgaurd, fatman brake, and a 3-9x40 vortex optic)..
At the moment most of the ammo I've shot comes on pretty close to the same (accuracy wise) in both guns. My most recent ammo tests results are below (I have the targets) and they were 5 shot groups ar 100 yards.


55gr Winchester m193
Rdb (3.18moa) Ar15 (3.25moa)

Fiocchi 62gr
Rdb (1.89) Ar15 (1.83moa)

 

[IAm_Not_Lost]

Speaking of the top rail being made of aluminum and causing POI shifts…..

anyone out there manufacturer a skeletonized steel top rail for the RDB? Would add a couple ounces, but wouldn’t be awful.

 

[odinforever2000]

Speaking of the top rail being made of aluminum and causing POI shifts…..

anyone out there manufacturer a skeletonized steel top rail for the RDB? Would add a couple ounces, but wouldn’t be awful.

Sadly no..

 

[Jojo Jaro]

A brilliant idea (I think) came to me.

How about cutting the barrel to just forward of the gas block and then threading it for a suppressor.

1. The barrel up to the gas block is .625", right?. So essentially cutting off the .561" portion of the barrel which would be the portion that would whip really hard since it is the end part and thinner.
2. Permanently weld a suppressor to extend the barrel pass 16" to avoid the $200 SBR commie tax. Or just thread it and pay 2x $200 commie tax - one for SBR and one for Suppressor
3. The foreend grip handguard could then be cut shorter if the suppressor is too big to slide into the plastic hand guard.

This will have the following advantages:

1. You will get a cool rifle that would really look awesome with an suppressor
2. You will get a shorter rifle overall compared to the Stock plus suppressor. Lighter, smaller, quieter and easier to maneuver in close quarters which I believe would be the predominant battlefield when SHTF.
3. The heavier suppressor would presumably reduce whip since it is heavier.
4. Heavier barrel reducing whip would definitely improve accuracy.
5. Heavier front end would improve RDB balance.
6. Overall, you will get what you really wanted (a short, lighter and suppressed rifle)
7. Perfect for when SHTF.


What do you guys think? Am I erroneously assuming something?

 

[Jojo Jaro]

[



Well, I have an RDB Survival and an RDB Hunter. The Hunter has a 0.625” barrel under the handguard - and to just forward of the gas block - and then tapers to 0.557” at the 18” mark of the barrel (I cut my 20” barrel down). The RDB Survival has a barrel thickness of 0.552” under the handguard and 0.475” just forward of the gas block and is consistent until the muzzle.

So, if someone has the regular RDB that they can measure……we can know all the barrel profile thicknesses.

And yes, I thought the 20” Hunter barrel was thicker, but now that I measure it, it is about the same as a light to medium contour AR barrel. I guess compared to the true pencil barrel of the Survival model it looks a lot bigger…..

Who cut and threaded your barrel? How much did you pay for that service? Is he authorized to do SBR conversion or permanently weld a Stainless Steel suppressor?

If you did it yourself, how much would you charge to cut down the RDB17 barrel and implement the Idea I posted above?

 

[IAm_Not_Lost]

Who cut and threaded your barrel? How much did you pay for that service? Is he authorized to do SBR conversion or permanently weld a Stainless Steel suppressor?

If you did it yourself, how much would you charge to cut down the RDB17 barrel and implement the Idea I posted above?

So, there is nothing wrong with your idea, but most people would rather pay the 200 bucks for the form 1 sbr than have one of their suppressors permanently pinned and welded. The only functionality problem you could feasibly see would be having enough gas to cycle the gun after chopping a good chunk of the barrel off, although attaching a suppressor would certainly give a bit back.

I did the barrel work. The method I use, and have used for multiple barrels, is suboptimal. I do not have a lathe and so use an annular cutter to size the barrel after chopping it. I then use a threading die to cut the threads, and then a muzzle crowning tool to finish it off.

So, while hand tools like I have will work, you are taking a chance that it will end up non-concentric, so you really have to be careful. And no, kindly, I have no interest in doing work for others as I wouldn’t feel comfortable not having the best tools to do the job.

You could probably find someone to do it, especially if you showed a copy of a form 1. If you just want someone to chop the barrel below the legal length and then promise them you are going to pin and weld a muzzle device or suppressor I am honestly not sure what the process is for that, or if any gunsmith would have a concern legally.

 

[odinforever2000]

A brilliant idea (I think) came to me.

How about cutting the barrel to just forward of the gas block and then threading it for a suppressor.

1. The barrel up to the gas block is .625", right?. So essentially cutting off the .561" portion of the barrel which would be the portion that would whip really hard since it is the end part and thinner.
2. Permanently weld a suppressor to extend the barrel pass 16" to avoid the $200 SBR commie tax. Or just thread it and pay 2x $200 commie tax - one for SBR and one for Suppressor
3. The foreend grip handguard could then be cut shorter if the suppressor is too big to slide into the plastic hand guard.

This will have the following advantages:

1. You will get a cool rifle that would really look awesome with an suppressor
2. You will get a shorter rifle overall compared to the Stock plus suppressor. Lighter, smaller, quieter and easier to maneuver in close quarters which I believe would be the predominant battlefield when SHTF.
3. The heavier suppressor would presumably reduce whip since it is heavier.
4. Heavier barrel reducing whip would definitely improve accuracy.
5. Heavier front end would improve RDB balance.
6. Overall, you will get what you really wanted (a short, lighter and suppressed rifle)
7. Perfect for when SHTF.


What do you guys think? Am I erroneously assuming something?

As Iam_not_ lost already stated...Suppressors aren't really a thing lots of folks are doing right now and he correctly listed the reason why..
Additionally, Supressors are allowed only in 42 states..So That would leave some folks out...hopefully you live in a free state.
..Even with Efiles right now its still a rather long wait..
The weight balance of the RDB is actually over the pistol grip not biased behind it like the Tavor and MDR.A suppressor can make the rifle a lil more front, Which is fine but that where the balance will be with a suppressor (and no LPVO but a red dot) LPVO + Suppressor = very front biased (depends mostly on Optic and mount)

I don't think you'll have a rifle that works if its cut all the way flush to the gas block.
Even the guy I follow who made his own custom 7" barreled RDBK in 350 legend still has about 2-3 inches of barrel infront of the gas block (right before the suppressor is screwed in).

Actaully after looking at his work...You'll have to pay a gunsmith some money to get what you want done for probably end up as "Minimal gains." Especially if your paying them to make sure the rifle works in the manner you want configured..
Good luck

 

[Jojo Jaro]

As Iam_not_ lost already stated...Suppressors aren't really a thing lots of folks are doing right now and he correctly listed the reason why..
Additionally, Supressors are allowed only in 42 states..So That would leave some folks out...hopefully you live in a free state.
..Even with Efiles right now its still a rather long wait..
The weight balance of the RDB is actually over the pistol grip not biased behind it like the Tavor and MDR.A suppressor can make the rifle a lil more front, Which is fine but that where the balance will be with a suppressor (and no LPVO but a red dot) LPVO + Suppressor = very front biased (depends mostly on Optic and mount)

I don't think you'll have a rifle that works if its cut all the way flush to the gas block.
Even the guy I follow who made his own custom 7" barreled RDBK in 350 legend still has about 2-3 inches of barrel infront of the gas block (right before the suppressor is screwed in).

Actaully after looking at his work...You'll have to pay a gunsmith some money to get what you want done for probably end up as "Minimal gains." Especially if your paying them to make sure the rifle works in the manner you want configured..
Good luck

Good point. I didn't know that you have to leave a few inches in front of the gas block. Is this something that has been found to be essential to the true functioning of the barrel or that he simply ended up with that by chance. Did he state that it was a requirement for proper functioning or simply because he wanted it there for various reasons. I guess what I am asking is, has there been a case where somebody cut the barrel flush into the gas block and found that it would not cycle? If it does not work, it is only the price of a new barrel. A shorter suppressed rifle is worth it to me.

Regarding the suppressor, I consider that to be essential for my intended use of the rifle - as a SHTF rifle.

If the suppressor tips the balance of the rifle forward, wouldn't that be a good thing. Many people are complaining that they are not used to bullpups because it is back heavy. Maybe if you put a suppressor, it would balance and handle much more like an AR. That would also minimize recoil.

I will try my idea when I find a reliable gunsmith. I think I'll go with an SBR and suppressor commie tax instead of permanently welding it.

 

[odinforever2000]

Good point. I didn't know that you have to leave a few inches in front of the gas block. Is this something that has been found to be essential to the true functioning of the barrel or that he simply ended up with that by chance. Did he state that it was a requirement for proper functioning or simply because he wanted it there for various reasons. I guess what I am asking is, has there been a case where somebody cut the barrel flush into the gas block and found that it would not cycle? If it does not work, it is only the price of a new barrel. A shorter suppressed rifle is worth it to me.

Regarding the suppressor, I consider that to be essential for my intended use of the rifle - as a SHTF rifle.

If the suppressor tips the balance of the rifle forward, wouldn't that be a good thing. Many people are complaining that they are not used to bullpups because it is back heavy. Maybe if you put a suppressor, it would balance and handle much more like an AR. That would also minimize recoil.

I will try my idea when I find a reliable gunsmith. I think I'll go with an SBR and suppressor commie tax instead of permanently welding it.

..The Rdbs weight is actually balanced over the pistol grip. Probably because the rifle doesn't use a traditional trigger bar to trigger pack setup like everything else does.

Other bullpups are back heavy (x95,hellion,mdr,aug), just not the keltecs.Thus forward weight on those bullpups shifts the balance forward toward the pistol grip.

All the short rifles I've seen are not flush cut to the gas block (look at shorty Aks, Ars and Fals and youll see what I mean)..You need some barrel to create enough back pressure to reliable cycle the gun.

As for "if it doesn't work it's only the price of the barrel"...Keltec sells complete rifles and you'll pay for a complete rifle from them if you want a new barrel (if you were going with an Ar..yea..you could just get a new barrel)..This is something seen here with folks trying to just get the extendable stock or wanting the survival barrel.