[SpacemanFrank]

After seeing Lee's design I was inspired to design my own.

The core idea with this design is to create a semi-free floated handguard.

This is achieved by using a clamp that locks onto the barrel near the base. By moving all the forces as close as possible to the receiver deflection of the barrel should be minimised.

This is the aluminum extrusion I will using for the prototype:
http://www.rossmachineracing.com/ovaltube.html

Once I have a working prototype I would not be opposed to going into production with the design should enough interest materialize.

On that note let me know what y'all think! What changes/improvements would you make?

I need to put work into the model of the RDB itself as I move forward with this and other projects.

If anyone would like to collaborate in fully CADing out the RDB let me know.

-Frank

PS. I also made myself a throw knob for my Primary Arms 1 to 4 power scope yesterday:

 

[Pistol-Pete]

Looks pretty cool.

Some thoughts:

Probably makes sense to make sure there's access to a jam nut for the muzzle device

It looks like you left some space to adjust the gas, make sure there's enough.

Interested in seeing how sturdy that mounting setup will be.

 

[SpacemanFrank]

I 3D printed the hand guard last night to do a fit and feel test.

The over all I really like the feel of the hand guard. The fit particularly around the lower receiver and muzzle of the gun need work but I should be ready to print another fit test in a few days and order the aluminum extrusion to machine the functional prototype.

The muzzle device nuts will probably be accessible in the final version per Pete's suggestion. I just need to figure out some geometry I like.

This area needs quite a bit of work.

Let me know what y'all think. Any more suggestions? Wish list items?

-Frank

 

[arguy]

Ironically, I just posted on the bullpup section of arfcom looking for more info on RDB M-Lok HGs. My only .02 would be making sure its wide enough to nest a typical rifle can inside on the fs/brake.

I would def be interested in one if they get run.

Mark

 

[SpacemanFrank]

What diameter are most suppressors?

Wall to wall on the current design it is 1.25 inches.

-Frank

 

[Shady]

for a .223 I would bet most suppressors are 1.5+

 

[st381]

Aero Precision enhanced or quantum rails have a 1.73" interior diameter which is big enough to accommodate my Rugged Surge762 which is a .30 caliber suppressor. Most rifle suppressors are going to be right at, give or take, 1.5" in diameter. It looks to me like you could flare out the front 2" of length on the handguard to provide suppressor space plus room to mount it on the muzzle and still retain a slim profile for the remaining length of the hand guard. The flare out could also be a sort of built in hand stop for non suppressor users as well.

 

[Lee Majors]

Looks good. Always good to see options.

Out of curiosity, you're clamping onto the barrel forward of the receiver. We didn't look into it, but have you considered trying to clamp onto the receiver front instead?

 

[SpacemanFrank]

I got around to printing the second mock up last night:

The major change of this mock up is moving away from the aluminum extrusion to bent sheet metal. I needed to move away from the extrusion idea because I was unable to locate an of the shelf extrusion profile that I liked while having sufficient wall thickness to mill flats for the M-Lok mounting points. I also spent more time modeling up the RDB as a whole, though that part of this project still has a ways to go. If anyone would like to collaborate on CADing up the RDB please let me know.

Given the interest in ensuring the hand guard is compatible with most suppressors I decided not to extend the handguard as far forward.

https://dl.dropboxusercontent.com/u/3207174/bull****%20comprestion%20is%20bull****.jpg

There still seems to be some issues with my fit but definitely much better than my first go around. I need to spend some time tweaking the model soon.

Let me know what y'all think!

Lee, I did think about clamping to the rear trunnion instead of the barrel but I have not found a way that I think would work well for that. My gut is to try and tie into the handguard lug and middle barrel pin. But that would likely require permanent modification of the rifle, something that should be avoided if possible IMO. That said I have not looked into it much.

Thanks, Frank

 

[Lee Majors]

That's what I was thinking, but was also thinking that possibly that aluminum plate that's right behind the pic rail on the top of the rifle could be removed and something tied into that area that was combination plate / anchor point.

It was in the back of my head for future designs, but since you're working on free-floating, just something I thought I'd ask to really free-float the HG independent of the barrel.

Nice work, by the way! I've had a few people ask about extended rails for suppressor mounting options (those suckers get REALLY hot), and it looks like yours might better accommodate that interest.

 

[arguy]

I think the updated design is a step in the right direction. It might be the angle of the photo but it still looks like a bit protrudes over the flash suppressor at the top. My plan (haven't even bought my RDB yet) is to leave my Gemtech Trek T can on it. It is direct thread onto the 1/2-28 muzzle. Anything that is beyond the shoulder of the threaded muzzle would preclude me from threading the can on, forget about having clearance for a QD can.

 

[madriverarms]

Bumping this to see if the OP has any updates...

and yes this is my first post, I've been lurking more or less since 2011 but I just got an RDB-C that could use a FF handguard.

 

[SpacemanFrank]

Hey y'all,

I have been MIA for a bit as work, school and other projects have taken over my life. I have also lost quite a bit of motivation to do this project as my RDB has suffered from the notorious bolt pin failure.

I have all the parts to fix the RDB but I have just lost so much faith in rifle I don't really know if I will continue on this project.

As far as this project goes have found a sheet metal shop at is willing to work with me on this project, I have just not followed through given the reasons stated above.

Thanks, Frank

 

[Furluge]

What has caused you to lose faith in the rifle? A local shop has one in that I'd been considering picking up.

 

[AndrewK]

I have also lost quite a bit of motivation to do this project as my RDB has suffered from the notorious bolt pin failure.

Don't let it get you down - I was reading back in early posts where users were initially running into the problem and very confused trying to track down what was happening. Collectively they spent a lot of time trying to figure it out and getting it resolved so at least it's a fairly easy fix now and more easily identified.

I just took my RDB to the range today after a very long vacation from it. It's still fun to shoot but still feels somewhat "cheap" to me in terms of build components. I decided it was probably a good idea to jump back to this site and see if there are any new issues. Good to see more American ingenuity at work designing after-market parts for the platform.

I thought about going aftermarket on the handguard previously but didn't like the idea of giving anything up for what I saw as benefits to the factory handguard.

 

[evi1joe]

I hope you keep working on it. Maybe someone could source stronger bolt pins as well. I know a lot of the CZ Scorpion aftermarket places have come out with IMPROVED replacement parts as well as aftermarket handguards and grips, etc.
I'm rooting for you all!!!
I prefer the squared off look (or a very slight angle) to the current options. The key is to get in before Midwest Industries and KT move in with their options, which may or may not be better.

 

[IamScotticus]

Me likes. Just leave room for A2 mount suppressors

 

[Jimfish67]

Well I would certainly be interested in one if you continue with the project OP!

 

[RuvinWolf]

Another bump for updates. I really want the RDB to succeed, and seeing people in the process of making aftermarket parts excites me. You can't have innovation without failure (Kel-tec is a shining example of this), and I think KT is on to something with this design. I just think it needs a bit more tweaking to really get off the ground.

 

[William Samuel]

I got around to printing the second mock up last night:

The major change of this mock up is moving away from the aluminum extrusion to bent sheet metal. I needed to move away from the extrusion idea because I was unable to locate an of the shelf extrusion profile that I liked while having sufficient wall thickness to mill flats for the M-Lok mounting points. I also spent more time modeling up the RDB as a whole, though that part of this project still has a ways to go. If anyone would like to collaborate on CADing up the RDB please let me know.

Given the interest in ensuring the hand guard is compatible with most suppressors I decided not to extend the handguard as far forward.

https://dl.dropboxusercontent.com/u/3207174/bull****%20comprestion%20is%20bull****.jpg

There still seems to be some issues with my fit but definitely much better than my first go around. I need to spend some time tweaking the model soon.

Let me know what y'all think!

Lee, I did think about clamping to the rear trunnion instead of the barrel but I have not found a way that I think would work well for that. My gut is to try and tie into the handguard lug and middle barrel pin. But that would likely require permanent modification of the rifle, something that should be avoided if possible IMO. That said I have not looked into it much.

Thanks, Frank

Any more work on this I love the design