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Posted: 7/7/2025 11:06:57 AM EDT
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I have in my head that I want a delayed 9mm upper for my registered receiver. Which 9mm system would you pick as an upper for a registered receiver? A similar question. Now consider a lightning link. Exact same question, but using the lightning link in an appropriate receiver after bolt modification. If y’all tell me that going delayed isn’t worth the trouble and I should just go straight blow back, that’s helpful. |
Words fall from your mouth like shit from ass.
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I have played with a bunch of different 9mm AR designs in full auto, including with RLLs. Everybody I know that bought a CMMG 9mm radial delayed unit, they all ate ejector springs. Depending upon the ammo, suppressor use and the specific spring you could destroy an ejector spring in as little as a couple hundred rounds or they could maybe last upwards of 1500ish rounds. I think everybody I knew who had a CMMG Radial 9mm to use with a machinegun got sick of replacing ejector springs and sold the upper off. The Maxim RDB Buffer didn't do much. The ROF was really high, recoil was high, and it made the gun a bit more difficult to charge. Not terribly difficult to charge but with an OEM standard charging handle you could notice the difference. That said, I was honestly surprise at how little it actually worked in making the gun a better shooter. The Scheel roller delayed system does work but by the time you put enough spring in the buffer to really cut down on recoil the gun becomes a "mortar the buttstock on the ground" proposition to charge. It seems like a delicate balancing act to get enough delay to make a meaningful difference and not have to be a gorilla to charge it. It does work much better than the Maxim buffer though. I have also played with the Kynshot hydraulic buffers and the associated weights. If you add a bunch of the Kynshot weights plus their hydraulic buffer it actually works to cut the recoil down but all that reciprocating mass makes the gun feel really choppy in auto. I have not played with the Mean Arms or the JP delayed 9MM guns due to cost and questionable compatibility with full auto and/or a RLL. There is also Amphibians CMMG Dissent Radial Fixed Ejector plus Kynshot hybrid I have no personal experience with but have considered building one of these days to try out. So far the best option I have found is to use a Kynshot hydraulic buffer and build a dedicated AR15-SD upper using a standard blowback design but in combination with a MP5 style ported barrel and an MP5SD style suppressor. Between the barrel porting and the hydraulic buffer it is actually a pretty nice combo. (they are generally really quiet as well) |
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Originally Posted By jbntex: Everybody I know that bought a CMMG 9mm radial delayed unit, they all ate ejector springs. Depending upon the ammo, suppressor use and the specific spring you could destroy an ejector spring in as little as a couple hundred rounds or they could maybe last upwards of 1500ish rounds. I think everybody I knew who had a CMMG Radial 9mm to use with a machinegun got sick of replacing ejector springs and sold the upper off. Originally Posted By jbntex: Everybody I know that bought a CMMG 9mm radial delayed unit, they all ate ejector springs. Depending upon the ammo, suppressor use and the specific spring you could destroy an ejector spring in as little as a couple hundred rounds or they could maybe last upwards of 1500ish rounds. I think everybody I knew who had a CMMG Radial 9mm to use with a machinegun got sick of replacing ejector springs and sold the upper off. The Maxim RDB Buffer didn't do much. The ROF was really high, recoil was high, and it made the gun a bit more difficult to charge. Not terribly difficult to charge but with an OEM standard charging handle you could notice the difference. That said, I was honestly surprise at how little it actually worked in making the gun a better shooter. If you look at that thread, I found a home for my Maxim RDB and that was with my FM9 belt fed upper. Works great with that. I have not played with the Mean Arms or the JP delayed 9MM guns due to cost and questionable compatibility with full auto and/or a RLL. There is also Amphibians CMMG Dissent Radial Fixed Ejector plus Kynshot hybrid I have no personal experience with but have considered building one of these days to try out. Many of us have MP5's and prefer this over the MP5. Very smooth with a nicer cyclic rate than the MP5. I did all that before CMMG finally released the FE (Fixed Ejector) Banshee in Feb 2025. I still think my PhaseII is still superior as discussed in my link above but not everyone wants to tune as much as I do and for most people I think getting a FE upper will satisfy most people. I have also been getting several people buying the FE Banshee retrofit kit which consists of the proprietary BCG and upper with the fixed ejector then getting an RDB barrel from me for less money and then they get whatever rail and CH they want. I go over all the 9mm M16 options I know of here: https://c3junkie.com/?page_id=361 |
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Originally Posted By amphibian: I did all that before CMMG finally released the FE (Fixed Ejector) Banshee in Feb 2025. I still think my PhaseII is still superior as discussed in my link above but not everyone wants to tune as much as I do and for most people I think getting a FE upper will satisfy most people. I have also been getting several people buying the FE Banshee retrofit kit which consists of the proprietary BCG and upper with the fixed ejector then getting an RDB barrel from me for less money and then they get whatever rail and CH they want. I go over all the 9mm M16 options I know of here: https://c3junkie.com/?page_id=361 I had no idea they released this fixed ejector retrofit kit earlier this year. I figured the uppers with the fixed ejectors were all still that dual recoil spring buffer-tube-less design. That makes things much easier vs. making my own carrier extension, making my own fixed ejector, and modifying an upper to take a fixed ejector. Seems like the way to go to buy the retrofit kit, a barrel and then a normal looking handguard, etc. vs. CMMGs starship-troopers looking handguard on the Banshee FE complete uppers. How is your radial 9mm barrel different from a radial barrel direct from CMMG? |
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Originally Posted By jbntex: I had no idea they released this fixed ejector retrofit kit earlier this year. I figured the uppers with the fixed ejectors were all still that dual recoil spring buffer-tube-less design. That makes things much easier vs. making my own carrier extension, making my own fixed ejector, and modifying an upper to take a fixed ejector. Originally Posted By jbntex: I had no idea they released this fixed ejector retrofit kit earlier this year. I figured the uppers with the fixed ejectors were all still that dual recoil spring buffer-tube-less design. That makes things much easier vs. making my own carrier extension, making my own fixed ejector, and modifying an upper to take a fixed ejector. 1. Lighter mass with the aluminum CE 2. I can do an extended stroke where the BCG doesn't bottom out for a super smooth impulse 3. I can tune the CE with live mass vs using dead weight like the Banshee BCG's use. I find using live mass to be much more effective.  Before the general public got their hands on the FE Banshee, I was curious to see if they would sell it with the 50 degree bolt like the old spring loaded ejector Banshee's or if they were going to use the same 55 degree bolt they use in the Dissent which is bufferless and has less mass. I was kind of surprised they went with the same bolt....Of course that makes more sense so they don't have to make two different bolts but I would think it may be an issue for people NOT running suppressed and using cheap 115Gr ammo. I have already seen posts and people complaining of just that. Some people are having reliability issues with that configuration. Most of my customers run suppressed like me. I have had a couple that want to run 115Gr unsuppressed and they run fine with my PhaseII when using it empty for the lightest weight setup.  How is your radial 9mm barrel different from a radial barrel direct from CMMG? I reference 3 links to threads where people are having issues with factory CMMG barrels. I too had issues with first barrel barrel but my second one was fine. I'm not saying they are all bad, just that they have been hit or miss. Some of those threads are not that old discussing this. I have been modifying straight blowback barrels but I am currently having a run of barrels made now out of stainless blanks that provide great accuracy. I like stainless for pistol caliber as I don't think you can wear out a stainless 9mm barrel even in full auto. It also makes it easy for me to deal with custom lengths or threads and not have to be concerned with any refinishing. I really don't like side chargers but I did below in hopes that my teenage son may find it easier to deal with vs a traditional charging handle location.  I'm using one lug for extended stroke and left more material high on the front lug to interface with the op rod.  |
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Thanks for all the information. Honestly, it’s a bit overwhelming in the choices. Especially @amphibian. I did some more reading with stuff I found and all the links here. This is what I’d like to have done. This is for a receiver AND lightning link use (obviously different lowers), mainly LL. Delayed upper with porting like a mp5-sd with an appropriate suppressor. Since it’s ported as such, I’ll have to use the suppressor or the yet to be released deflector (I’ll have to post the link later, but it’s on ar15.com) 100% of the time. If I go with the CMMG FE and the phase 2 mods, can you modify the carrier for LL use? Or do I need to send that out? I tinker until it works fine for my use, then I leave it alone. |
Words fall from your mouth like shit from ass.
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Originally Posted By Steamedliver: Thanks for all the information. Honestly, it's a bit overwhelming in the choices. Especially @amphibian. I did some more reading with stuff I found and all the links here. This is what I'd like to have done. This is for a receiver AND lightning link use (obviously different lowers), mainly LL. Delayed upper with porting like a mp5-sd with an appropriate suppressor. Originally Posted By Steamedliver: Thanks for all the information. Honestly, it's a bit overwhelming in the choices. Especially @amphibian. I did some more reading with stuff I found and all the links here. This is what I'd like to have done. This is for a receiver AND lightning link use (obviously different lowers), mainly LL. Delayed upper with porting like a mp5-sd with an appropriate suppressor.  I have customer running a PhaseII in full auto using a BRT ported barrel which has so many ports in it, he is running my aluminum CE with no internal weights to keep the weight down like I'm doing pictured above. For muzzle cans, I like a spring loaded weight inside. Since it's ported as such, I'll have to use the suppressor or the yet to be released deflector (I'll have to post the link later, but it's on ar15.com) 100% of the time. If I go with the CMMG FE and the phase 2 mods, can you modify the carrier for LL use? Or do I need to send that out? The other option is you get the CMMG FE Retrofit kit and then have someone machine it for the link and may also need to make some additional holes to lighten up the carrier more. |
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Suppressor adapter. |
Words fall from your mouth like shit from ass.
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