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[ARCHIVED THREAD] - Full Auto CMMG Guard Tuning (Page 4 of 4)
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Quoted:
Dare I ask...will we get to see the fixed ejector set up? |
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Thank you for the slow-mo comparison. It's awesome to watch the cases eject out of the AR more slowly than the MP5. It is quite an education. Thanks to everyone for being patient as I attempt to soak it all in. |
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So looks like CMMG has released a .40SW Guard now. What is strange is that I don't see it on their website yet but it is apparently out in peoples hands already and doing a Google search already listed on dealer websites. Here is a Youtube video of someone reviewing it: https://www.youtube.com/watch?v=4owYkXB2QAk Around the 4:40 mark he comments on how it works saying the tiny spring in the bolt carrier delays the unlocking.....I don't think he knows what he is talking about.....that spring is mainly to stop slamfires. His terminology is also all jacked up. He also says regarding the bolt, 'unlike a PCC which just has a flat surface'....WTF??? PCC could be straight blowback AR, Sig MPX, MP5, UZI...etc... Review would be much better if he kept his mouth shut. Anyways, I pulled some frames off the video that I thought were interesting. First is the ejector design: 
A new rounded ejector for 40SW? Note that RMW extreme used to cut angles on the 45 Gas operated uppers ejector to help kick the brass out properly. Maybe CMMG is trying something similar w/ this profile. Also maybe it is just me, but the lugs look like the angle isn't as sharp as a 9mm Guard...more like the cuts I've put on my 5.45 bolts... 
Lastly, thought I'd mention that I have full auto MIni and full size UZI bolts made by BarrelXchange years ago where the bolt face works with both 9mm and 40SW.... So, this new 40SW bolt may work for 9mm. Before seeing this video, I have actually been thinking about doing a 40SW Guard as I have a lot of 40SW brass that I want to get rid of. I think I may wait till they have a barrel / BCG combo available. I also have my Guard lower I'm not using since I switched to Endomags. I'd put that to use if I had a 40SW setup. Interesting stuff... >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ETA: See this on their Facebook page: >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> March 4 at 7:54 AMRadial Delayed Blowback has expanded to a new caliber. Check with your local dealer to order the new Banshee or Resolute chambered in .40 S&W. These will start shipping and be available to order on our website on March 26, 2019 |
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@amphibian
With respect to the "firing pin" spring, the video narrator is not incorrect, nor are you. The spring serves dual purposes. See, for example, paragraphs [0074] and [0075] with reference to FIGS. 7, 12, and 13 in the CMMG published patent application linked: http://pdfaiw.uspto.gov/.aiw?PageNum=0&docid=20180142972&IDKey=B42DE2FE6590&HomeUrl=http%3A%2F%2Fappft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPG01%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.html%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D%25252220180142972%252522.PGNR.%2526OS%3DDN%2F20180142972%2526RS%3DDN%2F20180142972 MHO, YMMV, etc. |
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@amphibian With respect to the "firing pin" spring, the video narrator is not incorrect, nor are you. The spring serves dual purposes. See, for example, paragraphs [0074] and [0075] with reference to FIGS. 7, 12, and 13 in the CMMG published patent application linked: |
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So...just updated my website with some more data:
Link below goes to the newest stuff. http://c3junkie.com/?page_id=538#section4 Some tidbits...for those that are too lazy to click on the link above: I'm testing the .40SW Guard bolt for use in 9mm. Notice the angle difference of the .40SW vs 9mm. 
Adding the suppressor and works. 
New rounded ejector design. 
I've put more comments on my website with some theories etc.... |
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@amphibian
@Esox Thanks to these 2 amazing members and the knowledge they bought share freely. Thanks to the community here as well. I have a working Guard 9mm with a rLL. I test fired it tonight ONLY for function and it was great. I used the set up amphibian recommends and LL tuning by Esox. I’m using the updated Mean Mags, without any modification. Single, auto and lock back all worked fine for my testing of 50 rounds (one box). It works. |
I’m over 3000 rounds on my cmmg radial delayed upper, shot almost entirely full auto on a colt post sample lower with the endomag conversions. I’m using an a5h2 buffer and tubbs spring. The only time it has malfunctioned is with super weak ammo while being really dry/dirty. About 1000 rounds were suppressed with a dead air wolf 9sd. I was initially worried about ejector spring life but it just keeps going and going.
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Quoted:
I'm over 3000 rounds on my cmmg radial delayed upper, shot almost entirely full auto on a colt post sample lower with the endomag conversions. I'm using an a5h2 buffer and tubbs spring. The only time it has malfunctioned is with super weak ammo while being really dry/dirty. About 1000 rounds were suppressed with a dead air wolf 9sd. I was initially worried about ejector spring life but it just keeps going and going.  https://www.youtube.com/watch?v=lFTG_-OtMRI
https://i.imgur.com/8tdUfpg.jpg If that is the case, I'm suspecting that maybe it is inconsistent headspacing. What happens if you load a dummy round then try to push on it with a metal rod? Does the bolt freely travel a bit like all 3 of my RDB builds do? I just got a custom barrel made where I had the barrel headspaced to remove that slop but haven't tested it yet. |
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Quoted:
I’m over 3000 rounds on my cmmg radial delayed upper, shot almost entirely full auto on a colt post sample lower with the endomag conversions. I’m using an a5h2 buffer and tubbs spring. The only time it has malfunctioned is with super weak ammo while being really dry/dirty. About 1000 rounds were suppressed with a dead air wolf 9sd. I was initially worried about ejector spring life but it just keeps going and going. https://www.youtube.com/watch?v=lFTG_-OtMRI
https://i.imgur.com/8tdUfpg.jpg |
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That is great to hear. Did you compete at the last KCR SMG match with it? Chili17 posted on Uzitalk that a couple guys were running CMMG RDB setups saying they didn't have any ejection issues either with 3-4k rounds. http://www.uzitalk.com/forums/showthread.php?91585-CMMG-banshe-on-RR-questions/page3 If that is the case, I'm suspecting that maybe it is inconsistent headspacing. What happens if you load a dummy round then try to push on it with a metal rod? Does the bolt freely travel a bit like all 3 of my RDB builds do? I just got a custom barrel made where I had the barrel headspaced to remove that slop but haven't tested it yet. And sorry, no dummy rounds. |
amphibian is definitely the number 1 salesperson of guard/banshee platforms. Thanks to his guidance I finished my build today. Only did 350 rounds all suppressed but so far trouble free and it groups like a MANIAC with my 135gr loads.
I don't know if I should add the weights to the carrier or not as I'm not blessed with full freedom. Instead I'm merely working in fullsemi auto. Everyone's thoughts? |
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amphibian is definitely the number 1 salesperson of guard/banshee platforms. Thanks to his guidance I finished my build today. Only did 350 rounds all suppressed but so far trouble free and it groups like a MANIAC with my 135gr loads. https://i.imgur.com/99kLYAs.jpg I don't know if I should add the weights to the carrier or not as I'm not blessed with full freedom. Instead I'm merely working in fullsemi auto. Everyone's thoughts? Are you happy with the suppression? I've posted about Tom Bower's stating that the 5" was loud to him. I haven't heard a 5" in person. I think CMMG's recommendation is to add the 2oz weight when using a suppressor. I don't like the weights as it just adds more reciprocating mass. Are you running my preferred buffer/tube/spring setup now? |
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amphibian is definitely the number 1 salesperson of guard/banshee platforms. Thanks to his guidance I finished my build today. Only did 350 rounds all suppressed but so far trouble free and it groups like a MANIAC with my 135gr loads. https://i.imgur.com/99kLYAs.jpg I don't know if I should add the weights to the carrier or not as I'm not blessed with full freedom. Instead I'm merely working in fullsemi auto. Everyone's thoughts? On the weights: Have the tuning kit but haven't needed it. All good. |
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As others have said I am running the carbine buffer with a simple silicone coated carbine spring in a carbine buffer tube. This setup allows me to run everything from the same lower from 556 to 300 blackout.
The suppressor is a silencerco ASR. It is much much quieter then the blowback equivalent which actually hurts your right ear when you shoot. I would go as far as to say that it is MP5 quiet. I sent you an email asking about weights I didn't see that you already answered my question amphibian thank you. The suppressor is about 9 in Long. The blast chamber is a full 3 inch. I suppose the suppressor probably has a lot to do with how quiet the system is. your friend that said it's loud I would hazard a guess and say that he should probably run a different suppressor. Or maybe try running it wet. |
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As others have said I am running the carbine buffer with a simple silicone coated carbine spring in a carbine buffer tube. This setup allows me to run everything from the same lower from 556 to 300 blackout. Quoted:
As others have said I am running the carbine buffer with a simple silicone coated carbine spring in a carbine buffer tube. This setup allows me to run everything from the same lower from 556 to 300 blackout. We have been trying to get some quantitative data on the recoil with various buffer configurations. I had my partner mill out a rifle length buffer tube so I could use a high speed camera to watch what the spring and buffer look like as well as watch the rearward and forward movement on the gun. All firing at high speed was done on a lead sled to minimize the 'human factor'. 
The buffer tube / buffer and spring setup that I recommend runs great on mag fed 5.56 and 300BLK also. Video below is the 9mm CMMG with the CMMG recommended buffer/spring configuration....which basically sounds like what you are using. Again, all filming was done from a lead sled, strangely, it would run 100% from the shoulder but would jam in the sled.... Again better than straight blowback but not MP5 smooth.  8" 9mm CMMG RDB factory config Now my preferred configuration with my modified 5.45 bolt to optimize the delay for suppressed usage....since this bolt was optimized for 147gr suppressed usage, it doesn't lock back on the last round when a suppressor is not mounted and running 115gr. (the factory CMMG 9mm bolt would lock back fine with this ammo but I didn't get a high speed video of this configuration yet). I also forgot to put my 300BLK Tubb spring in there. It will lock back with that spring UNsuppressed....I'll do a vid of that next time. I think you can clearly tell the improvement in the recoil impulse going to the hydraulic buffer and flat spring in these videos over the CMMG recommended buffer/spring.  8" 9mm CMMG RDB, mod'd 5.45 bolt, UNsuppressed, fixed ejector RB5007 Adding the suppressor and going to 147Gr in this video.  8" 9mm CMMG RDB, mod'd 5.45 bolt, suppressed, fixed ejector RB5007 The suppressor is a silencerco ASR. I sent you an email asking about weights I didn't see that you already answered my question amphibian thank you. Again, comparing to the MP5 gold standard - not much reciprocating mass there. Control cyclic rate and smoothness by changing locking pieces on that platform not throw mass at the problem....while I modified the bolt lug angles on the CMMG RDB. I don't want to go to lightening the carrier so I'm left with modifying the stroke length and the buffer / spring variations which I did a lot of testing over the weekend on this and may post later about... The suppressor is about 9 in Long. The blast chamber is a full 3 inch. I suppose the suppressor probably has a lot to do with how quiet the system is. your friend that said it's loud I would hazard a guess and say that he should probably run a different suppressor. Or maybe try running it wet. He used to own subguns.com and posted his experience on his forum before those boards were taken over by Frank and now barely anyone goes there these days. I suspect he was at some CMMG sponsored event as he also stated that he tried the CMMG branded 'Defcans' and said it didn't make a difference. I asked him if he tried the 8" version and he said he didn't and that he would think it would quieter than the 5". |
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I don't want to go to lightening the carrier so I'm left with modifying the stroke length and the buffer / spring variations which I did a lot of testing over the weekend on this and may post later about... But now I'm wondering if using a mod'd bolt with more aggressive angles would make a difference? At least enough to make it worth chopping up the carrier again? |
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Awhile ago, I tried using a shortened (lighter) carrier in a 'bufferless' franken Guard but found recoil to be incredibly sharp & snappy (this was using a stock bolt & 8" barrel). I failed to take into account the lighter carrier was producing higher velocities when traveling rearward toward my shoulder (total reciprocating weight was ~11.7oz). So even though the action was 'delayed', its still blowback and thus benefits from some amount of mass to absorb the initial impulse. I sighed in failure and welded the carrier back together. But now I'm wondering if using a mod'd bolt with more aggressive angles would make a difference? At least enough to make it worth chopping up the carrier again? Quoted:
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I don't want to go to lightening the carrier so I'm left with modifying the stroke length and the buffer / spring variations which I did a lot of testing over the weekend on this and may post later about... But now I'm wondering if using a mod'd bolt with more aggressive angles would make a difference? At least enough to make it worth chopping up the carrier again? Did you just chop it right after the autosear trip like what Dead Foot Arms does? Like this? 
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strangely, it would run 100% from the shoulder but would jam in the sled.... |
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That is very interesting and unexpected. Could have an effect on buffer test results. Data may show that clamping down the pivot arm cancels whatever is causing that to happen. Still haven't had time to look at the data but def will get to it today. Quoted:
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strangely, it would run 100% from the shoulder but would jam in the sled.... |
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Yeah...that is what I'm hoping....I definitely wouldn't do the lightened carrier without the modified bolt angles.... Did you just chop it right after the autosear trip like what Dead Foot Arms does? Like this? https://deadfootarms.com/wp-content/uploads/2017/06/BOLT-CARRIER-GROUP-DLC-1.jpg 
I cut it forward of the original trip then welded new trips on the bottom with plans to make a sear trip bar similar to the MPX/MCX. I'm temped to try it again with a mod'd bolt but think the recoil will still be sharp. |
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Close: https://i.imgur.com/h98Y7Eo.jpg I cut it forward of the original trip then welded new trips on the bottom with plans to make a sear trip bar similar to the MPX/MCX. I'm temped to try it again with a mod'd bolt but think the recoil will still be sharp. Quoted:
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Yeah...that is what I'm hoping....I definitely wouldn't do the lightened carrier without the modified bolt angles.... Did you just chop it right after the autosear trip like what Dead Foot Arms does? Like this? https://deadfootarms.com/wp-content/uploads/2017/06/BOLT-CARRIER-GROUP-DLC-1.jpg https://i.imgur.com/h98Y7Eo.jpg I cut it forward of the original trip then welded new trips on the bottom with plans to make a sear trip bar similar to the MPX/MCX. I'm temped to try it again with a mod'd bolt but think the recoil will still be sharp. Also, I would think you would have bolt bounce issues in full auto with setup unless you have some other means to mitigate that? |
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Amphib, emailed you bud.
Can't argue with the high speed. Can we get some licensed or official MP5 footage shot from the same person as a reference? Not empirical, but close as we can get. I'll earmark the a5/kynshot buffer next time I buy parts. Thanks for your hard work. |
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Can't argue with the high speed. Can we get some licensed or official MP5 footage shot from the same person as a reference? Not empirical, but close as we can get. I'll earmark the a5/kynshot buffer next time I buy parts. Thanks for your hard work. If you look at the other threads I referenced, I was already planning on doing a high speed of the MP5 from the same lead sled. Again, trying to use the sled to minimize the human factor so it shouldn't really matter who is pulling trigger...although I will most likely be the one doing the shooting again. |
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I have a little over 1000 rounds through my 5" 9mm upper without a single issue. Every round was suppressed except 5 for testing purposes. No real wear to speak of on the lugs or bolt face and the ejection is still strong and piles neatly to my 4 o'clock about 5 feet away.
Carbine buffer tube, silicone coated spring, and standard carbine buffer. Primary load is a 135gr coated RN, travelling at 1000 FPS. I've also shot a few random 147s here and there and it has chambered and eaten everything so far. I'm very pleased at this point. |
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Quoted: What happened to the big long CMMG RDB thread in the PCC section? It disappeared from my subscriptions list and I can't seem to find it. Am I just blind? https://www.ar15.com/forums/AR-15/Thoughts-on-the-CMMG-Guard-/15-713060/?page=25 |
[ARCHIVED THREAD] - Full Auto CMMG Guard Tuning (Page 4 of 4)
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