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Posted: 9/8/2023 11:59:10 AM EST
[#1]
Quote HistoryOriginally Posted By Mad-Machinist: Not trying to be a smart ass.....but with an unlocked action headspace isn't really possible to check. Do not decieve yourself, at no time is an RDB action ever locked. When I make RDB barrels I make then like a make DI barrels, with a locking bolt. It seems to work as I have done quite a few with out complaint. Can't you run Go/No-Go gauges in straight blowback pistols? Never used one before, nor tried to check, but if the action has an OOB safety, shouldn't the NoGo gague & OOB safety prevent the hammer/striker from falling? |
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MO, USA
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Posted: 9/12/2023 7:36:43 PM EST
[#2]
Reached out to CMMG for an updated bolt. They said they would send one out. Fingers crossed it works better.
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MO, USA
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Posted: 9/23/2023 4:11:45 PM EST
[#3]
New bolt arrived. Time to start the shot counter and see how long it lasts.
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Posted: 9/24/2023 11:57:11 PM EST
[Last Edit: chevrofreak]
[#4]
My girlfriend and I shot 2 matches last weekend and both of our CMMG's crapped the bed. Neither rifle had over 300 rounds on their current ejector spring. I broke down today and bought her a Dissent upper to see if it will be more reliable.
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FL, USA
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Posted: 9/25/2023 11:28:58 AM EST
[#5]
Quote HistoryOriginally Posted By chevrofreak: My girlfriend and I shot 2 matches last weekend and both of our CMMG's crapped the bed. Neither rifle had over 300 rounds on their current ejector spring. I broke down today and bought her a Dissent upper to see if it will be more reliable. |
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Posted: 9/25/2023 12:03:11 PM EST
[#6]
Quote HistoryOriginally Posted By amphibian: That sucks...have you considered the JP-5? I have, and I have 2 of them configured on the JP site and just haven't pulled the trigger. I built a new PCC for competition use with the Maxim RDB buffer and it talked me out of spending the money on a JP. Unfortunately both CMMG PCC's were being used by my girlfriend when they had repeated malfunctions. We had a day match, followed by a night match and during the day match my girlfriend's rifle jammed so bad that she had to quit a stage and unfortunately got DQ'd when she AD'd the rifle during unload and show clear. The spent, unejected case remained on the bolt face, and fed another cartridge into the chamber. When she cleared the spent case, the gun would not chamber another round and she did not think to rack the bolt without a magazine inserted to ensure the chamber was clear, and when she dropped the hammer fired a round into the ground in front of the target array. During the night match she ran my rifle with a suppressor and ended up having the same failure to extract problems that plagued her during the day match. Needless to say, she was very frustrated. We both have other PCC's, but our CMMG's are SBR's and that is what she prefers shooting in matches. |
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FL, USA
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Posted: 9/25/2023 12:20:46 PM EST
[#7]
Quote HistoryOriginally Posted By chevrofreak: I have, and I have 2 of them configured on the JP site and just haven't pulled the trigger. I built a new PCC for competition use with the Maxim RDB buffer and it talked me out of spending the money on a JP. Unfortunately both CMMG PCC's were being used by my girlfriend when they had repeated malfunctions. We had a day match, followed by a night match and during the day match my girlfriend's rifle jammed so bad that she had to quit a stage and unfortunately got DQ'd when she AD'd the rifle during unload and show clear. The spent, unejected case remained on the bolt face, and fed another cartridge into the chamber. When she cleared the spent case, the gun would not chamber another round and she did not think to rack the bolt without a magazine inserted to ensure the chamber was clear, and when she dropped the hammer fired a round into the ground in front of the target array. During the night match she ran my rifle with a suppressor and ended up having the same failure to extract problems that plagued her during the day match. Needless to say, she was very frustrated. We both have other PCC's, but our CMMG's are SBR's and that is what she prefers shooting in matches. Quote HistoryOriginally Posted By chevrofreak: Originally Posted By amphibian: That sucks...have you considered the JP-5? I have, and I have 2 of them configured on the JP site and just haven't pulled the trigger. I built a new PCC for competition use with the Maxim RDB buffer and it talked me out of spending the money on a JP. Unfortunately both CMMG PCC's were being used by my girlfriend when they had repeated malfunctions. We had a day match, followed by a night match and during the day match my girlfriend's rifle jammed so bad that she had to quit a stage and unfortunately got DQ'd when she AD'd the rifle during unload and show clear. The spent, unejected case remained on the bolt face, and fed another cartridge into the chamber. When she cleared the spent case, the gun would not chamber another round and she did not think to rack the bolt without a magazine inserted to ensure the chamber was clear, and when she dropped the hammer fired a round into the ground in front of the target array. During the night match she ran my rifle with a suppressor and ended up having the same failure to extract problems that plagued her during the day match. Needless to say, she was very frustrated. We both have other PCC's, but our CMMG's are SBR's and that is what she prefers shooting in matches. I don't think I've seen anyone post any feedback on the JP-5. I don't think I've seen anyone post on the Dissent either. (not including Youtube influencers, talking here on ar15.com). Good luck with the Dissent and hope to you post some feedback on it. Since it has a fixed ejector, I would assume you would be GTG. |
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Posted: 9/25/2023 12:27:06 PM EST
[#8]
Quote HistoryOriginally Posted By amphibian: That sucks...As you may have seen me post before, I think the JP-5 looks awesome and I would buy one if it was full auto compatible but the ejector sits right where the sear needs to go and I confirmed with JP that it wouldn't work. I am still testing the MEAN Arms which I have running pretty good now but still need to see how many rounds it will go before it too starts having extractor / ejector spring failures. I don't think I've seen anyone post any feedback on the JP-5. I don't think I've seen anyone post on the Dissent either. (not including Youtube influencers, talking here on ar15.com). Good luck with the Dissent and hope to you post some feedback on it. Since it has a fixed ejector, I would assume you would be GTG. Since I had it sitting in my cart for a couple of days before ordering, CMMG emailed me a 10% off coupon. At $1305 shipped for a Sniper Grey 6.5" upper that will match her registered lower I couldn't pass it up. I will try to post feedback about the reliability compared to the Banshee's. |
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PA, USA
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Posted: 10/3/2023 5:42:58 PM EST
[#9]
Does anyone have a high round county 5.7 or 4.6 rdb? Did they have the spring issues? Did they use the same spring?
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MO, USA
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Posted: 10/4/2023 6:17:01 AM EST
[Last Edit: Joedirt199]
[#10]
Lots of JP5 chatter over on the BrianEnos forum under their pistol caliber carbine section.
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Posted: 10/16/2023 12:39:28 AM EST
[#11]
Quote HistoryOriginally Posted By amphibian: Good luck with the Dissent and hope to you post some feedback on it. Since it has a fixed ejector, I would assume you would be GTG. We've had a chance to run the Dissent upper a bit, and so far so good. The ejection is very positive, tossing cases at least 10ft even with some of my light loaded 135gr subsonic. My girlfriend was doing fast, accurate double and triple taps that put a huge grin on her face. She shot it back to back with her Banshee and she likes the Dissent so much more. I don't know if the 6.5" barrel vs 8" barrel makes much difference l, but I agree with her that the Dissent is more fun to shoot. It sounded awesome suppressed, too. The down side is that you *have* to use their included end plate, which will prevent you from swapping uppers around unless whatever upper you put on uses a forward side charging handle. I ended up ordering a Glock mag lower that we are going to SBR to alleviate the other problem she has, of not being able to easily seat the Endomag on a closed bolt, even when downloaded. |
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Posted: 10/30/2023 12:36:23 AM EST
[Last Edit: Alien]
[#12]
My home built 9mm RDB gun ran a lot better with the heaviest weight and BCM extractor upgrade, but the failures still reared their head at the end of my session (which was surprising when it happened because it was fine before that). I swapped the ejector spring after my last outing where I had a few failures to extract. The factory spring was slightly shorter than the spares/replacements I ordered from CMMG a while back. I'm hoping that this solves the issue. I'll be taking her back out next weekend.
Edit: I finally got out to shoot. I only wound up shooting a couple of mags through it, but no malfunctions with the RDB with the new ejector spring, BCM extractor upgrade kit, and heaviest BCG weight. I might try and reduce the BCG weight to the lightest one and see how it performs next time since it might not be necessary if the ejector spring was the issue.  |
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TN, USA
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Posted: 11/11/2023 8:34:45 AM EST
[#13]
I bought a 9mm bolt and barrel kit this summer. My bolt is marked 50, so apparently it's the new bolt. The gun ran fine for 200 rounds, all suppressed. Yesterday, the ejection issue reared its ugly head. I pulled the bolt and there's very little tension on the ejector. So no, the new bolt and MK10 spring did not solve the issues.!
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PA, USA
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Posted: 11/11/2023 9:45:10 PM EST
[#14]
What buffer weight and bcg weight is everyone running? Is the ejection issue potentially related to bolt speed? CMMG recommends a H1 buffer I have heard, but I personally haven't seen this literature. In the RDB manual pdf I have it only references buffer weight with the MK10 10mm platform. In the 9mm AR platforms in general we use reciprocating mass to reduce recoil, but can this have the negative side effect of reducing ejection reliability aswell? Does having a lower reciprocating mass/higher bolt speed make the system more "punchy" but increase ejection reliability?
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TN, USA
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Posted: 11/12/2023 9:35:10 AM EST
[#15]
Quote HistoryOriginally Posted By SSTPAC: What buffer weight and bcg weight is everyone running? Is the ejection issue potentially related to bolt speed? CMMG recommends a H1 buffer I have heard, but I personally haven't seen this literature. In the RDB manual pdf I have it only references buffer weight with the MK10 10mm platform. In the 9mm AR platforms in general we use reciprocating mass to reduce recoil, but can this have the negative side effect of reducing ejection reliability aswell? Does having a lower reciprocating mass/higher bolt speed make the system more "punchy" but increase ejection reliability? I'm using a H2 buffer. It ejects about 4:30. An H1 would probably be better, as it wont lock back on empty using subs and a H2 buffer. I put a new 5.56 ejector spring in it yesterday and fired 60 rounds without issue. Based on my experiences, Id say bolt speed is not the issue. |
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FL, USA
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Posted: 11/12/2023 2:17:58 PM EST
[#16]
I ordered mine in June of 2019 and haven't had to replace anything as of yet. Knock on wood... I shoot a couple hundred rounds once a month or so when my wife and I go to our local range. I do use Amphibian's 300blk flatwire and RB5007 buffer upgrades though. It's a 5" barrel SBR and is only shot suppressed. I guess I have something to look forward to...
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Posted: 11/13/2023 6:11:34 PM EST
[#17]
I don't see how the problem can ever be eliminated with the ejector spring......short of a redisign with a fixed ejector. Having the ejector push the rim to front of the extractor groove and then having it slam against the bolt face when fired compressing the spring in milliseconds is probably exceeding the capability of the spring. Perhaps an extractor with a thinner groove that holds the case closer to the bolt face would help, but that has the drawback of possibly inpacting reliable feeding and the ability of the case to roll off/out of the extractor groove on ejection.
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Posted: 11/13/2023 8:24:48 PM EST
[#18]
Quote HistoryOriginally Posted By Mad-Machinist: I don't see how the problem can ever be eliminated with the ejector spring......short of a redisign with a fixed ejector. Having the ejector push the rim to front of the extractor groove and then having it slam against the bolt face when fired compressing the spring in milliseconds is probably exceeding the capability of the spring. Perhaps an extractor with a thinner groove that holds the case closer to the bolt face would help, but that has the drawback of possibly inpacting reliable feeding and the ability of the case to roll off/out of the extractor groove on ejection. That's exactly what they went to when they did their ARish bufferless design. |
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TN, USA
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Posted: 11/14/2023 5:48:19 AM EST
[#19]
Quote HistoryOriginally Posted By Mad-Machinist: I don't see how the problem can ever be eliminated with the ejector spring......short of a redisign with a fixed ejector. Having the ejector push the rim to front of the extractor groove and then having it slam against the bolt face when fired compressing the spring in milliseconds is probably exceeding the capability of the spring. Perhaps an extractor with a thinner groove that holds the case closer to the bolt face would help, but that has the drawback of possibly inpacting reliable feeding and the ability of the case to roll off/out of the extractor groove on ejection. What effect would too stiff an extractor spring have on the ejector spring, if any. In my.gun, which wore out the ejector spring around 200 rounds, it is very difficult to move the extractor at all. There is considerably more wear on the extractor face than one would expect from such a low round count. |
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FL, USA
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Posted: 11/14/2023 3:02:32 PM EST
[#20]
Quote HistoryOriginally Posted By molar: What effect would too stiff an extractor spring have on the ejector spring, if any. In my.gun, which wore out the ejector spring around 200 rounds, it is very difficult to move the extractor at all. There is considerably more wear on the extractor face than one would expect from such a low round count. If you remove the suppressor, it will not extract though. I guess some could also argue on the type of suppressor, ammo etc...whatever...I'm just saying in my configuration this is what happens. My point is that not much extraction force is needed when suppressed which is 99% of my shooting. |
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Posted: 11/14/2023 3:44:33 PM EST
[#21]
Quote HistoryOriginally Posted By amphibian: If you look at page 1 of this thread and the second video I posted, I prove that if you completely remove the extractor from the bolt of a suppressed CMMG RDB it will extract on it's own. In fact, I ran a match of around 500 rounds where the extractor pin was broken and the extractor was just flopping around in there and it never missed a beat. Didn't even know till I went home to clean it and the pieces fell out. If you remove the suppressor, it will not extract though. I guess some could also argue on the type of suppressor, ammo etc...whatever...I'm just saying in my configuration this is what happens. My point is that not much extraction force is needed when suppressed which is 99% of my shooting. Quote HistoryOriginally Posted By amphibian: Originally Posted By molar: What effect would too stiff an extractor spring have on the ejector spring, if any. In my.gun, which wore out the ejector spring around 200 rounds, it is very difficult to move the extractor at all. There is considerably more wear on the extractor face than one would expect from such a low round count. If you look at page 1 of this thread and the second video I posted, I prove that if you completely remove the extractor from the bolt of a suppressed CMMG RDB it will extract on it's own. In fact, I ran a match of around 500 rounds where the extractor pin was broken and the extractor was just flopping around in there and it never missed a beat. Didn't even know till I went home to clean it and the pieces fell out. If you remove the suppressor, it will not extract though. I guess some could also argue on the type of suppressor, ammo etc...whatever...I'm just saying in my configuration this is what happens. My point is that not much extraction force is needed when suppressed which is 99% of my shooting. Given the action depends on the cartridge pushing the bolt to work, that it would run w/o an extractor isn't very surprising. |
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TN, USA
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Posted: 11/15/2023 7:29:24 PM EST
[#22]
Quote HistoryOriginally Posted By amphibian: If you look at page 1 of this thread and the second video I posted, I prove that if you completely remove the extractor from the bolt of a suppressed CMMG RDB it will extract on it's own. In fact, I ran a match of around 500 rounds where the extractor pin was broken and the extractor was just flopping around in there and it never missed a beat. Didn't even know till I went home to clean it and the pieces fell out. If you remove the suppressor, it will not extract though. I guess some could also argue on the type of suppressor, ammo etc...whatever...I'm just saying in my configuration this is what happens. My point is that not much extraction force is needed when suppressed which is 99% of my shooting. It seems like the more tension on the extractor, the stiffer the ejector spring needs to be to overcome. Would that be safe to assume? |
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FL, USA
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Posted: 11/15/2023 9:33:15 PM EST
[Last Edit: amphibian]
[#23]
Quote HistoryOriginally Posted By molar: It seems like the more tension on the extractor, the stiffer the ejector spring needs to be to overcome. Would that be safe to assume? Dummy round in chamber. Imagine when the round is detonated and you have this much slop between the lugs of the bolt and barrel extension. Like hitting a brick wall, that is what is killing the ejector springs. Do this same test with an MP5 and this doesn't happen there is no slop. I tested my new MEAN Arms bearing delay and it doesn't do this either.  9mm CMMG RDB Headspacing Again, I had a custom barrel made with no slop but then it isn't violent enough to work with the spring loaded ejector and now you must have a custom fixed ejector like I did. |
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TN, USA
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Posted: 11/15/2023 10:32:42 PM EST
[#24]
Quote HistoryOriginally Posted By amphibian: I don't think it really matters in regards to the ejector spring life. Again, video I posted on page 1 pasted below. Dummy round in chamber. Imagine when the round is detonated and you have this much slop between the lugs of the bolt and barrel extension. Like hitting a brick wall, that is what is killing the ejector springs. Do this same test with an MP5 and this doesn't happen there is no slop. I tested my new MEAN Arms bearing delay and it doesn't do this either.  https://www.youtube.com/watch?v=xhm4omLtW2sAgain, I had a custom barrel made with no slop but then it isn't violent enough to work with the spring loaded ejector and now you must have a custom fixed ejector like I did. Interesting. My recent manufacture barrel and bolt doesnt have much slop at all it seems, but the ejector spring still wore out after a couple hundred rounds |
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VA, USA
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Posted: 11/21/2023 10:03:58 AM EST
[Last Edit: Gotterdammerung]
[#25]
Mean Arms just announced "exomags" that will work with their Bearing Delay upper and the CMMG RDB. They will come in 10,15,20,32 and 40 round capacities.
Exomags |
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FL, USA
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Posted: 11/21/2023 11:06:34 AM EST
[#26]
Quote HistoryOriginally Posted By Gotterdammerung: Mean Arms just announced "exomags" that will work with their Bearing Delay upper and the CMMG RDB. They will come in 10,15,20,32 and 40 round capacities. Exomags |
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Posted: 11/21/2023 11:08:40 AM EST
[#27]
Quote HistoryOriginally Posted By amphibian: Thanks! I just pre ordered a 10 pack. Hope they are reliable. I just ordered a 10 pack of the 40 rounders myself. I hope they seat more easily on a closed bolt. |
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NV, USA
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Posted: 11/23/2023 12:08:08 PM EST
[#28]
Quote HistoryOriginally Posted By Mad-Machinist: I don't see how the problem can ever be eliminated with the ejector spring......short of a redisign with a fixed ejector. Having the ejector push the rim to front of the extractor groove and then having it slam against the bolt face when fired compressing the spring in milliseconds is probably exceeding the capability of the spring. Perhaps an extractor with a thinner groove that holds the case closer to the bolt face would help, but that has the drawback of possibly inpacting reliable feeding and the ability of the case to roll off/out of the extractor groove on ejection. As far as I can tell (I've been following this for years) there is not a solution the RDB ejector problem except for a fixed ejector. Is it possible that you can create a fixed ejector solution and offer it to RDB owners? I feel this would be a viable product with a lot of orders. |
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Posted: 11/23/2023 1:37:03 PM EST
[#29]
Quote HistoryOriginally Posted By BartCarter: As far as I can tell (I've been following this for years) there is not a solution the RDB ejector problem except for a fixed ejector. Is it possible that you can create a fixed ejector solution and offer it to RDB owners? I feel this would be a viable product with a lot of orders. I would buy that. |
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