problems just popped up with the radial delayed bolt

[BartCarter]

31 minutes ago, bwikel said:

Anyone trying to install the extra power extractor spring make sure you aren't trying to use the original plug or an o-ring. With the larger diameter end of the spring down on the bolt you should be able to lay the extractor on top of it then compress it in the middle and insert the pin. 

 

No insert or o-ring is the installed preference for certain extra power extractor spring providers like Tubbs.  But the instructions for BCM does not state that, only that the o-ring is optional.

[BartCarter]

As promised, here are a couple of pics. I put pressure right above the pivot pin.  Line everything up 1st and then a light press and the pin slips right in.

 

I am using Knipex parallel pliers with no teeth, just a flat, straight surface.  There are other pliers out there, but I like the range of adjustment with the Knipex.  You can probably rig something up with other pliers and something to protect the surfaces.

 

 

[MemphisMechanic]

@Salsantini @BartCarter I did the same thing that Bart did, I simply used a small clamp instead of pliers . 
 

@SergioSF... Here’s where my ejection port ended up. Hogged it out with a carbide burr on a dremel, then cleaned it up with a selection of hand files.

 

The ejection port on a factory Guard upper (which is what I’m running!) is already widened. 
 

Because I was having erratic ejection from cases bouncing off the rim of the opening, I chose to go the extra mile and really open it up. I also extended it forward until you can see a bit of the barrel extension.

 

I did this early on while building this franken gun to attempt to fix issues that were magazine-height related back when I was running colt mags. It didn’t help at the time, but I’m glad I did it because I’ll never wonder if a small port caused a malfunction.

 

 

Edited January 4, 2020 by MemphisMechanic

[Les Snyder]

mine was opened up from.500 to .640"... I wanted to retain the dust cover (we get occasional rain), so my cut started just in front of the dust cover latch, and down to the dust cover rod...a 1/4" carbide cutter opened up the corners a little, but not as much as MM...doesn't really look like much, but the height was increased 28%

[Salsantini]

6 hours ago, MemphisMechanic said:

@Salsantini @BartCarter I did the same thing that Bart did, I simply used a small clamp instead of pliers . 
 

@SergioSF... Here’s where my ejection port ended up. Hogged it out with a carbide burr on a dremel, then cleaned it up with a selection of hand files.

 

The ejection port on a factory Guard upper (which is what I’m running!) is already widened. 
 

Because I was having erratic ejection from cases bouncing off the rim of the opening, I chose to go the extra mile and really open it up. I also extended it forward until you can see a bit of the barrel extension.

 

I did this early on while building this franken gun to attempt to fix issues that were magazine-height related back when I was running colt mags. It didn’t help at the time, but I’m glad I did it because I’ll never wonder if a small port caused a malfunction.

 

 

Looks Like The Grand Canyon!  Thanks for posting the pics.  

[SergioSF]

@BartCarter thank you for that! I need to find a pair of those pliers. I’ve been trying to do it with just my thumb and index finger all this time... 

 

@MemphisMechanic  I think you meant to respond to Les about opening the port, but that was helpful to see.  Thank you. BTW, I dig that cerakote.

 

[Les Snyder]

Memphis and all, again thank you... the RDS ran well at the match Sunday, the shooter had a slight problem pre flighting the carbine... first time in 35 years that I've had a sight come completely off...just the extra power spring seemed to do the trick...

[bwikel]

On 1/1/2020 at 8:15 AM, Les Snyder said:

Memphis...one more thing if possible... can you give me the ejection port height dimension for the factory Guard upper?  I think I may chuck it in the milling machine at some point... thanks

 

I don't think this got answered but the factory guard ejection port opening is about 0.62 in. I don't really see a need to open up the port if the extractor and ejector are working correctly. 

[cking]

The CMMG RDB is having problems with FTE, turns out it is the ejector spring, it destroys them in less than 1000 rounds. Drift over AR15.COM . CMMG will send you a heavy ejector spring, as for a new roll pin because it will killed the one in there. Nobody knows why it Kills springs

[Les Snyder]

cking... I've been in on part of the AR15.com discussions... I think there is a distinct difference between the problems the full auto set up amphibian (arfcom) has been discussing and the USPSA PCC problems I encountered... I am having good results since removing the hardened elastic plug inside the ejector spring...I did replace the extractor spring as Memphis recommended, but I'm really leaning toward the inability of the extractor to slip over a cartridge rim due to the hardened inner plug to be the cause of my problem

 

 my ejector does not bottom out the spring when depressed to the bolt face depth, and since there is no direct hot impingement gas  transferring excessive heat to the carrier, heat should not really be a problem... the 9mm bolts should run considerably cooler than a 5.56

[cking]

I'm not running full auto and the two other shooters I know are not either.

 

I disagree on extractor making it over the rim, bolt would not lock. 

 

I'm running the biggest spring and plug I can get in my extractor and after playing with moving the extractor further in made things worse.

 

I took the contrary view and clipped my ejector spring and polished the ejector and still not reliable.

 

So now I'm back to new springs in ejector and extractor, using silicone chrome. We see how long the ejector spring lasts.

 

Asked CMMG to send the new heavy ejector spring. But have no idea why the ejector spring fails so quickly. I've checked with roll pin out that ejector can't drive the spring to solid. However the roll pin is ready to fail and beat flat about the same time as the spring fails.

 

At a total loss how such light pin as the ejector is beating up the  ejector spring up and the roll pin. It is not heat or running solid. 

[Les Snyder]

OK... sounds like we have/had different problems... my problem originally looked like a double feed, and I looked at the magazines that had worked flawlessly for a couple of years without finding a solution.. live round in chamber, and another live round forced up between the bolt face and top of the receiver ... when I pulled the bolt apart the hardened plug was discovered... since removing it, the carbine has run about 400 rounds (two matches and a little function testing without a problem....I did not notice any wear or battering problems with the roll pin holding the ejector.... regards

[MemphisMechanic]

@cking @Les Snyder

 

My sequence of events:

 

Began having issues with empty brass inside the upper when the bolt returned forward several times per mag. Facing all kinds of different directions.

 

Played with ammo PF and buffer spring. Destroked gun. No change.

 

Replaced ejector spring with a factory AR-15 5.56 one. No change.

 

Replaced extractor spring with a BCM extra power one, which I clipped a coil off of for some reason I forget. Gun began to choke MUCH more often.

 

Installed a factory BCM extra power extractor extractor spring, using a C-lamp to align everything while inserting the pin. 1,500 rounds since then without a jam. Including returning to lighter PF (140pf 147s) ammo, and a heavy buffer and spring.

 

Edited February 3, 2020 by MemphisMechanic

[Les Snyder]

to follow up... my RDB is paired with an Enidine hydraulic rifle length buffer and stock rifle length recoil spring ... I shoot an A1 (Vietnam era) stock on both the PCC and my 3 gun AR...I was originally concerned that the ETS magazine followers would not clear the bolt lugs on an inserted but empty magazine ... in practical application the 40 round ETS magazines work fine, and I get a slight scraping on the next round to be presented, and if shot dry, will place a small scrape on the follower... I had problems at the match yesterday using the Magpul 27s with a 3D printed extension... had a baby rattler when the follower did not negotiate the transition (which was slightly beveled)... so will use the factory base 17 round MagPuls for reload mags, and the 27s for shorter stages

 

at this point I'm pretty happy with the RDB system... I get very little dot movement ( 142pf Bayou 135s with 3.4 WSF) hydraulic buffer and modified Miculek brake...

at 72 , astigmatism, overweight, and arthritic knee, I'm not going to win any matches, but still like to have my equipment work... if I screw up, I can live with that ... regards, and again, everyone thanks for the replies

[cking]

Here is the reply today from CMMG

We have changed the ejector and extractor springs in those. We are currently waiting a shipment of the extractor springs. As soon as we get those in, I can send you replacements.

 

 

 

 

Joe Dodson. Technical Support Representative
CMMG, Inc. | PO BOX 68 | Boonville, MO 65233
Tel: 660.248.2293 Ext. 322 | Fax: 660.248.2290
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