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After I removed the thread protector from the RDB-C, I noticed that the threads stopped at least a half an inch from the end. Does anyone know the reason for this? I have several Muzzle Brakes and none of them will look right with this awkward setup.

Does Keltec sell a muzzle brake to cover this up? Is there a way to extend the threads to the end so that AR brakes can be utilized?

 

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The brake on this is a Shrewd #2, slightly tapped to accept the threaded end, and a chopped section of the collar behind it to cover the proprietary thingie I'll never use.

You can substitute pretty much any brake you want this way (in case you didn't want a ten foot barrel like my weird setup), but it's obviously not a 'plug and play' solution

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After I removed the thread protector from the RDB-C, I noticed that the threads stopped at least a half an inch from the end. Does anyone know the reason for this? I have several Muzzle Brakes and none of them will look right with this awkward setup.

Does Keltec sell a muzzle brake to cover this up? Is there a way to extend the threads to the end so that AR brakes can be utilized?

I'm not an RDB owner, but it sounds like the muzzle thread pitch is the same as an AR15 (1/2"x28RH)? If so, you might consider a modified 'reverse' or 'slip-over' flash suppressor. They're most commonly made with a 3/4" ID unthreaded sleeve, about 3" long or so, that slips over the barrel; the threaded section is close to the muzzle end, with an A1 type flash hider extending out from the muzzle. The design is supposed to make a standard 16" barrel look more like a short XM-177 barrel with long flash hider attached. If you're ok with an A1 flash hider (they're actually pretty effective), you could shorten the unthreaded sleeve to an appropriate length, and it would cover that gap.

Just an idea; FWIW, YMMV, etc.
 

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After I removed the thread protector from the RDB-C, I noticed that the threads stopped at least a half an inch from the end. Does anyone know the reason for this? I have several Muzzle Brakes and none of them will look right with this awkward setup.

Does Keltec sell a muzzle brake to cover this up? Is there a way to extend the threads to the end so that AR brakes can be utilized?

I think that space was meant for their proprietary folding iron sight like they have on the survival models. I wish they'd sell that sight separately. I've seen older pics of the C model with those folding sights on them.
 

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You can also use these from ultradyneusa.com/product-category/accessories to cover the rest of the muzzle end instead of the lock nut that I used:
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I contacted them and confirmed the inner diameter, but chose to go with the one piece lock nut to cover it.

You'll also want to, and will probably need a Muzzle Device Alignment Shim Set: https://www.amazon.com/dp/B01FZLM2A4/ref=dp_cerb_2
 

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Its a Bi!*# to get that damn stock muzzle thread protector off if you dont heat if with a torch of some sort first also!
 

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A shim set is only needed if backing the MD against a hard shoulder, like the barrel face and it needs to stop in a certain position (its index). Since Its nearly impossible to match the MD and barrel threads perfectly to get a perfect MD position (indexing), shims are used to create the stop point for the right index. Then a thread lock will be needed.
A hard backing is often necessary for MDs that are mounts for other devices like cans.

Jam Nuts don't require shims. If using a jam nut, screw the JN all the way back, the MD back to the JN, rotate the MD forward to the index point, tighten the JN up against the MD. Thread lock is optional, but still a good idea since a JN is more likely to work loose than a crush washer.

Using a crush washer, the CW has enough tension on the MD to not need thread lock. A CW will usually have enough compression to allow a half turn of the MD against it for indexing. If not, use shims behind the CW to space it forward. But if you have to do that, a JN is better. CWs are very popular since they do two jobs, but they aren't reusable.

Timing for accuracy is a whole different matter, but I highly doubt timing will make any difference with these rifles. I would like to see someone prove it does.
 

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a shim set is only needed if backing the MD against a hard shoulder, like the barrel face. Since Its nearly impossible to match the MD and barrel threads perfectly to get a perfect MD position (indexing), shims are used to create the stop point for the right index. Then a thread lock will be needed.

Using a jam nut, screw the JN all the way back, the MD back to the JN, rotate the MD forward to the index point, tighten the JN up against the MD. Thread lock is optional.
That's what I thought, but it looks like he has both the jam nut and a shim in the posted pics.
 

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Shims are thin washers, very hard to see.
You might be looking at a sleeve or collar. IDK.

Now that I actually look at Spencer's pictures, I think he has a crush washer between the JN and MD. He's using the JN to cover the threads and space the MD forward so the crown isn't too far into the MD.
He could have done the same thing with sleeves, but he has the utility of a JN if needed. Smart.
 

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After I removed the thread protector from the RDB-C, I noticed that the threads stopped at least a half an inch from the end. Does anyone know the reason for this? I have several Muzzle Brakes and none of them will look right with this awkward setup.

Does Keltec sell a muzzle brake to cover this up? Is there a way to extend the threads to the end so that AR brakes can be utilized?

Hello just making sure , what is the thread pitch for this rifle
 

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After I removed the thread protector from the RDB-C, I noticed that the threads stopped at least a half an inch from the end. Does anyone know the reason for this? I have several Muzzle Brakes and none of them will look right with this awkward setup.

Does Keltec sell a muzzle brake to cover this up? Is there a way to extend the threads to the end so that AR brakes can be utilized?

Remove the stock thread protector cut off the threaded side leave the length .650(5/8+), put back on the gun and now the ar break will thread down and stop. Adjust the .650 length for timing. Refinish the threaded left over so you can protect the thread if you remove the break.
 
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