Seems like a great solution, but after calling CMMG, it doesn't seem like they have any plans to support select fire lowers.  Would a modified Hahn block work? Anyone tried?

Do you know / did they say what specifically was incompatible?

Do you know / did they say if it works with a RDIAS?

@amphibian

I was unable to get it to work with a RR. However these are my variables.

1.  Geissele trigger
2.  Endo Mags
3.  Cmmg Banshee in 9mm.

I have two CMMG Guard 8" barrel/BCG combos built out on two different uppers.
I bought a second set after initial testing of my first set was positive.  I am planning on having the barrel turned down for an old SD type can I've had laying around for years.

I also bought their Glock lower with the first combo as a baseline setup to make sure it works with that.
I used Aero Precision 458 Socom uppers for both since they have the enlarged ejection port for the different ejection pattern of this system.

I used a RDIAS with their lower to get a baseline.
Buffer system testing of that configuration is here: http://c3junkie.com/?page_id=538

After that, I moved on to modifying my Hahn mag block to work with unmodified Colt mags.  
That is detailed here: http://c3junkie.com/?page_id=597

What I found was that the Colt mags require more force to strip rounds than the Glock mags and was only reliable if I increased the buffer spring strength which increased my RoF in full auto and I didn't want to do that.

So now that the Endomags are out and I received mine Thursday and tested great on Saturday: https://www.ar15.com/forums/ar-15/Anyone-seen-this-MEAN-Arms-9mm-adpater-/15-728601/&page=8

Below is a link to a video from Saturday with the Guard and the Endomags with my two 8" Guard uppers.  
https://www.youtube.com/watch?v=_XaGtM2NT38

I'm really hoping Mean arms does an Endomag for 40 round Pmags!!!

Awesome. So it seems you confirm the guard system works with DIAS?? Any limits? Works with their Guard Upper and Guard Glock Mag lower?

Yep...got it working in 3 different scenarios in FA.
1. Guard Glock lower and RDIAS
2. M16 lower, unmodified Colt mags and modified Hahn mag block and modified mag catch
3. M16 lower and Endomags.

Awesome.

How would you compare it to 9mm blowback AR? Fully tuned, hydrolic, what not. Best of the best, just not the guard.

How would you compare it MP5?

Night and day difference to a blowback 9mm IMHO....I know some may argue that but I'm testing in full auto.  I think most people that can't tell a difference are running in semi.
I tried for years back around 2003 to get the 9mm Colt blowback to run smooth.  Best I could get was a ported SD setup, pneumatic buffer (that ended up leaking) and no weight in bolt.

If you look at my picture below taken from my site link above, you'll notice the MP5K PDW in the background that I was comparing too.

The MP5K PDW is slightly smoother BUT it is also so fast that it is extremely difficult to pull single round bursts on it....likewise, if I increase the RoF on the Guard it gets smoother.
The nice thing about the AR platform is that I CAN mess with various buffers/springs to tune it...No real tuning on an MP5 other than changing locking pieces.

This is a link to a stage at a SMG match I went to 2 weeks ago.

I had the selector set to Full the entire time.

You can see that I was pulling singles at will during this stage.

https://www.youtube.com/watch?v=M1xytZoYemk

I am not done tweaking and have some other things in mind that I hope work out.

I am chubbing up....

Do you not like the glock mag / guard glock lower? Which mag setup do you prefer and why? 2nd / 3rd, etc.

I see one of these coming real soon. I haven't yet gotten the CMMG 22lR to run FA, this seems like a ton of fun for pretty cheap... less headache.

1. While really new (just came out last week), I really like the Endomags.
I like leaving my Geissele SSF fire control in that one lower and have it work with everything.  If you've read my tuning links, you'll see that the buffer tube, buffer and spring configuration I'm using for the 9mm Guard is working out great for my 556 setups as well as the FM9 belt fed.
For any double feed mag, you can use the bump method and don't even need a loader.Endomags are obviously double feed.  Very easy to load.
Again, really hoping Mean comes out with a 40 round Endomag.

2. Glock mags have been proven to be very reliable.
For speed loading Glock mags, you've got the Maglula or the new ETS loader.

3. I've never liked Colt mags.  Hate them...but do have a lot of them.  All factory Colt and Metalforms and they will all 'volcano' on you if you bump them.  I don't care what anyone says, but I've had them fail on me on matches too many times.

It also comes down to training issue for me.
Pictured below is my dedicated suppressed 556 12.5 Mid with a Brevis II Ultra.

Same length as the 9mm Guard setup.  I know a lot of people are going with the 5" Guard setup but I wanted the 8" since I am more concerned with:
1. having more knockdown power for steel targets
2. having a configuration that is consistent with my 556 setup
3. Even my full size UZI's 3 lugged ~9" barrel is subsonic in FL.  I posted details on this at this thread: https://www.ar15.com/forums/AR-15/Which-9mm-pcc-Macon-CMMG-FM-ect/15-730602/

I use the same mag pouches if I'm running a SMG match or Rifle match.

If I didn't care to run rifle at all then maybe I'd just stick with the Guard Glock lower.  
I know could carry more mags in the same amount of space if I ran the Guard Glock lower...but I'm not trying 'game' it.  I'm not trying to be the fastest guy out there.  I just want to be as consistent as I can.

Also in regards to being consistent, I had already modded my Guard lower to have the PDQ like my regular MGI 556 magwell:
http://c3junkie.com/?page_id=583

He was kind of dismissive. He said it was designed to work with Glock mags, that was the whole point.  I asked about a Hahn block and he said those are for Colt SMG mags.  I didn't really push it but I don't think it would have gone anywhere.  Said it wasn't supported. I need to read everyone's posts in detail, but I don't see why the guard bcg wouldn't strip rounds off a Hahn block, just need to remove the ejector.  Great info here

I have also tested the CMMG system full auto with an RDIAS.  I have had near the same experience Amphibian has had and he has been a wealth of knowledge with his testing.  My baseline stock system was CMMG's Glock lower, bolt and 8" barrel.  I used a 458 socom stripped upper I found cheap and a BCM mlok carbine rail I already had.  The CMMG spec for buffer and spring was a .308 carbine length spring and standard CAR buffer.  Mine ran nearly 100% with that setup but it was fast and a little rough but still not as bad as a regular blow back 9mm AR.  I also tested an older colt pattern mag lower I had SBR'd years ago made by DDLES.  I had some modified Uzi mags and bought a Colt 9mm mag to try.  The mag or mag catch has the be modified to lower the magazine or the bottom lugs on the Guard bolt run won't clear.  That is probably why CMMG does not support it.  I modified an extra mag catch and got that running pretty well but had the same experience where a full mag had too much tension and bolt could not strip the round.  If I loaded to 25 rounds it ran fine.

Amphibian tested a slew of buffer and springs and found the Tubbs flatwire with the Knyshot/Blitzkrieg hydraulic buffer to be the softest/smoothest in an A5 extension.  It is for sure the combo to soften and slow the system down.  I was having a stoppage FTF about once or twice per mag with that setup.  CMMG have recently redesigned the BCG that should solve that so I am waiting on a replacement bolt group from them to test.  I got my MEAN arms adapters last week and they run just as well as the Glock lower for me also.  What is nice about the MEAN arms setup is you don't have to lower anything.  You order them from MEAN and tell them you are using them in a Guard and they come ready to go.  If my new bolt group solves the random FTF issue I will be very happy with this setup and would consider it a very close second to a full size MP5 in shooting feel.

I’ve heard about various changes CMMG has made to Guard components since they were released. I bought the 45 and 9mm kits as soon as they came out.  Any idea what they’ve changed?

I know they changed the extractor design.  Amphibian confirmed that in a side by side.  My bolt, barrel, and lower were from an April 18' ship date and we believe I had the newer extractor.  When I first contacted them they wanted me to try the .308 spring, carbine buffer, and some known ammo like Winchester white box.  It did run much better in that configuration maybe a fail to feed every other mag or so but still the same issue.  I contacted them again last week and they told me they have made more design changes and they wanted to swap my BCG completely.  They also no longer recommend a .308 carbine spring and since I had purchased that from them to test earlier this year they are sending me a new spring also.  Not sure which spring they are recommending now or what other bolt/bcg changes they have made.

no one has taken a cmmg banchee 9mm upper w/ mean mags and tossed it on a m16 yet???

im starting to wonder why they make uppers if they dont run out of the box on any gun other than theirs?...i guess they are for guard lowers for people who want 45 and 9mm and just want to swap uppers

wondering why they wouldnt make a ar/m16 upper that works with every ar/m16 lower (milspec)

its odd to me...a missed opportunity to sell thousands of these

I've already posted about my (2) 8" CMMG Guard uppers running on my M16 lower with Mean mags as well as posted the video.
I know it's not the Banshee but the only difference is 3" shorter barrel.

As you mentioned on the Geissele SSF, thread,
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Quoted:
$25k and cant spend $350 on a trigger?

your in a rich mans hobby.......people p*ss away thousands on extras...
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

25k and you can't spend $700 on another upper?

I've already shown that it works with the 8" barrel....In addition, before the Banshee came out people were already getting the 8" Guard and cutting the barrel down to 5" and working fine with Colt 9mm mags.  If it works with Colt mags it will definitely work with the Mean Endomags as less force is required to strip rounds off the Endomags than the Colt mags.

That is only the tip of the iceberg.  The  .45 Guard uses large frame Glock mags and the 9mm uses small frame Glock mags.  So there is no mix and match.  The Mutant 47 is such a great concept.  The .308 bolt has so much more strength for 7.62X39.  But CMMG based it on a shortened AR10 design instead of a standard AR-15.  So it is semi auto only as owners of AR-15 machinegun conversion devices (DIAS and LL) can't use the conversion device outside the "family" of firearms the conversion device was designed for.  So those conversion devices can't be used with the Mutant 47.  Apparently CMMG must think that they will make more money selling the complete semi firearms instead of making the systems to work with standard AR lowers so the full auto conversion devices can be used.

Scott

i thought you bought the barrel and bolt and put it in your own upper??? am i wrong on this? you didnt open the ejector hole to the same size as the CMMG

am i wrong on this??

here;s  your post i found

''Now that the 9mm Guard came out, I've been playing with it and so far I'm pretty happy with it.
I got just the 8" barrel and BCG combo and stripped Guard lower. As mentioned, I'm using a Tubbs flat wire 556 spring, A5 tube and Blitzkrieg/Kynshot hydraulic buffer. Very smooth. Very close to a full auto MP5K PDW.''
''

the 2 uppers above pictured...1 doesnt look like a cmmg at all..the other if it is has a different rail on it...

you took a cmmg guard out of the box, put it on your m16 and it worked with no mods?   if so why does CMMG say no-no to the idea when i asked them....they lost a sale

if i hear it works ill gladly toss $700 down on one...i want it to work BRO!........i just dont want to be the first to try...my lower is a govt marked m16a2....i dont want to break a $35k lower as an experiment

I think you are over complicating this.

I have a bunch of parts laying around and it made no sense for me to buy their upper when I already have spare upper receiver parts and charging handles.
I only needed the Guard specific parts which are the barrel and BCG which is $350 retail.

In regards to the upper, I just got a couple of these: https://www.aeroprecisionusa.com/458-socom-stripped-upper-receiver
That upper receiver's ejection port is clearanced more just like the Guard is.

So for $430 retail, I could get what I needed to do a Guard upper. The other parts are all standard AR parts...the rail and charging handle are standard so why should I buy those from CMMG and pay more for them to slap it together and use parts I already have on hand?

I don't think you read that post correctly...
The post with the two uppers is explaining why I want the 8" barrel and not the 5" barrel.  The top upper is using the Guard barrel and BCG.  The bottom upper is 5.56 12.5 Mid gas with Brevis Ultra II suppressor.

I've updated my post with the two uppers above and put descriptions on them so there is no confusion....
Do you expect CMMG to promote another company's product???   (MEAN Endomags....)

Guard upper (whether you build it yourself using their barrel+BCG or buy complete upper)
+ Mean Endomags
+ M16 lower
= working configuration w/ NO mods

All that said, I've been running the Guard with Glock, Colt and now the Mean Arms Endomags in full auto for a few months now.  I have posted on other threads that for some reason, the Guard seems to kill ejector springs rather quickly and when this happens you will start to have malfunctions.  I also broke both firing pins in both of my Guard uppers yesterday.  I don't know if they just got crappy firing pins or this is a design flaw.  I will be posting these details in another thread in a few and contacting CMMG.

so you did not buy a cmmg upper and toss it on your m16 and it ran

you bought parts, put them on someone elses upper and it works...

its not the same

i want it to work 100%....cmmg says it might not....you have a bolt/barrel on someone elses upper and it works....that doesnt tell me what i need to know....i dont want to be the first to experiment...id prefer others try it first....its shocking cmmg would make an upper not compatible with a m16 or colt AR......they are losing the market on everyone wanting to swap uppers and get a 9mm upper....but they want everyone to buy their complete gun.....i still find it odd they sell the upper separate and then say it wont work..........why not design it to work with an OEM/mil spec lower

You gotta be kidding me...you think that their:
1. upper receiver
2. rail
3. charging handle
Have magical pixie dust and assembled by elves or something?
You've never slapped AR parts together?

No, not the same as ordering a complete upper but mechanically, it IS the same....nothing magical about those 3 parts from the ones I sourced and me putting them together.
Again, CMMG isn't making money endorsing the MEAN Endomags...

If you read through the CMMG Industry forum you will get your answer.....
They already said that the reason they were selling the proprietary BCG and Barrel separately was to support those that wanted to do things themselves.  They know it can be made to work, there is no magic to it.

Now if CMMG made the Guard setup like the Sig MPX where it won't fit a standard AR lower that would really suck...but they didn't....fortunately uses standard geometry AR/M16.

i want to believe you...i really do....i just need someone to buy a upper and slap it on the gun

if its works why dont they tell me it does? their tech dept. said no guarantee....or did they even say no...i have to look back on their email

i dont know if their upper is special with pixie dust......i wouldnt be buying one and piecing it together...id like to buy the banchee and toss it on

i have stripped my M16a2 down to a bare receiver and tossed in all after market parts, but i have not built an upper..

i hope you are correct!!!!

ill wait for someone else to buy a banchee and report on it....then im all in

One step ahead of me again....my PDQ showed up yesterday.  Although the endo mag thing means I can use the boonie packer solution with the wire behind the bolt catch (I really like this system).
Maybe its further down...is there a thread FAQ on removing the ejector from the endomag?  I hear that sell them without now, but I don't see the option on their site.

I haven't seen that Boonie Packer solution...I do have a AXTS lower and looks like their was some patent infringement and they work the same...so you drop the mag and lock bolt back at the same time?  
I dont use my AXTS anymore since the PDQ came out as I prefer to have those functions seperate.
Mean arms sent me 3 Endomags for the Guard while I had another 6 arrive for blowback (incorrectly) I modified 5 more for the Guard (Easy with Dremel and disk sander).  I'll take some pics if u want.
I think it was in their 3rd Youtube video that they said to put you want the Guard version in the order notes section.

Just sold my blowback 9mm setup. Might check this out down the road

nevermind, i found the answer to my question upon further reading.

I have a 9mm blowback colt sytem and tried the endo mags. Got ejectors got chewed up. Wish I had known about the Guard coming out while back otherwise I would've skipped the blowback. Just gonna wait in hopes cmmg comes out with a shorter barrel combo. ~4.5" 3 lug barrel would be perfect. Running a Tros 5" right now. Would love a 9mm AR with 499rpm!

Don't know if you've seen this thread: https://www.ar15.com/forums/AR-15/Thoughts-on-the-CMMG-Guard-/15-713060/?page=12

I got my first 8" BCG/barrel combo when they were introduced and it seems there have been two things I know that changed for the 9mm Guard.  Both of which are detailed in the link above with pictures.
1.  I think they were initially using 556 extractors and now have changed to an extractor that is better contoured to jump over the rim of a 9mm round.
2.  The 45 Guard uses a proprietary ejector spring that is shorter but stronger than a 556 ejector spring.  The 9mm Guard came with the standard 556 ejector springs and  they have changed that.

I also mention in the link above about how both of the firing pins in my two Guard setups broke the same day and they are both relatively new BCG's as I had the original BCG swapped.  The verdict is out on that as I don't know if they just got substandard parts or if this is a design flaw.

After replacing the FP's and ejector springs, I have been back to 100%.  
When I got that 499 RPM that was with the 556 extractor and ejector and later had reliability problems and removed the 3.5 oz carrier weight.
I also think the 499 RPM with the 3.5 oz weight is a little bouncy

I mentioned my current setup at the bottom of my Guard testing page: http://c3junkie.com/?page_id=538

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
** Update, after more testing, I am removed the weight from the carrier which has increased my RoF.  Same buffer system:556 Tubb flat spring
9mm Blitzkrieg/Kynshot buffer
A5 length buffer tube

702 RPM

Same configuration as above using the Tubb 300BLK spring, I get 674 RPM but haven't done a significant amount of testing with that spring.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

In addition, I do have another idea I want to try and need to test and hope to have some results soon.

Anyways, good thing you didn't get in too early as I think the 9mm Guard system runs very well for full auto with the current gen extractor and stronger ejector spring.
If there is a weak point on the system, I would say the ejector spring.  A fixed ejector, mounted in the upper would have been great.  I mentioned that I worked on a prototype piston operated 9mm upper and we had the same ejection problems when we were using a 5.45 bolt (same bolt face diameter as a 9mm).  We thought we had to go to a fixed ejector in the upper and that would require some major surgery to the bolt and carrier...but if you look at the Sig MPX, that is basically what they had to do.
BTW, I also have a post sample full auto Sig MPX and like the Guard better as I don't like relying on the gas system for pistol caliber and the Guard suppresses better than the MPX and easier to tune.  MPX shoots too fast and not much you can do about it (I also have the 4 position gas regulator from ILWT on it as well).

All that said, if it turns out that the ejector spring is a wear item that needs to be carefully watched, I'd be willing to live with that.....I really don't care if it periodically eats firing pins either.  
Looking at the alternative to dropping +30K for an HK sear, I could just buy an extra complete BCG for swapping out.

Are the ejector, ejector spring, firing pin,and firing pin spring proprietary parts on the Guard, or can standard 223 AR15 parts be used as replacements?

ejector and FP are standard 223 AR15.

I already addressed the ejector spring in my previous post.

"2. The 45 Guard uses a proprietary ejector spring that is shorter but stronger than a 556 ejector spring. The 9mm Guard came with the standard 556 ejector springs and they have changed that. "

A standard 223 ejector spring works but will get worn out faster.

wow, okay, Amphibian delivered as always.  I let this thread baste in his glory and I'm not disappointed.  Okay, so basically Guard barrel/BCG, throw an upper on the CNC and machine out the ejection port, then pin it to my M16 lower with some endomags?  Profit?  If that's the case I'll throw my money at it right now!

Yes but you don't even need to CNC out the ejection port.  Just buy it already done from Aero or Anderson (458 Upper is already clearanced).
https://www.aeroprecisionusa.com/458-socom-stripped-upper-receiver
https://www.andersonmanufacturing.com/product/andersons-458-socom-stripped-upper-receiver/

I actually don't think the 9mm really even needs the clearanced upper (I know the 45 Guard and 45 DI uppers need it)...but got it anyways to be safe.

hmm 55 bucks... already have an upper... but I wouldn't need to cerakote... this is definitely easier.

I'm looking forward to this, not having to fire a paint shaker blowback 9mm would be my dream.

My impression after reading about how the Endomags work:



this thing looks like a total disaster waiting to happen.  Do these things actually work worth a damn?  $30 for a kit that doesn't include the mag.  Now, I have a ton of pmags just sitting around, but still.. this thing looks... questionable.

Has anyone tried the stern defense Glock adapter?

I'm really happy with my Endomags so far.
I like being able to use the same pouches as my standard M16 mags and not have to deal with a mag block.  Very easy to load as well.  Awesome to be able to just swap uppers and go...no mods to anything in the lower.
I really hope they come out with one that works with the 40 round Pmags.
If you look at the thread below, you'll see the issue I had was with the BHO engaging w/ 1 round left in the mag:
https://www.ar15.com/forums/AR-15/Anyone-seen-this-MEAN-Arms-9mm-adpater-/15-728601/?page=11

I've had a few cases where a round didn't feed...no jam, just didn't feed but I haven't had time to figure out if it is just 1 or 2 of the ones I have doing that.

Most people have positive results, most people with issues are all running straight blowback setups and having issues w/ the built in ejector.

In regards to the Stern Glock adapter, yes, someone posted using one in full auto with the Guard already....and I have a local friend that did it as well.  Like me, he had to TIG a blob under his BHO catch so it would engage it on the last round since the adapter needs to sit lower.  Obviously also need to remove the ejector from the adapter.

I personally don't like the new mag release location on the Stern.

I do like the idea of not having to push a mag block in and out, but I have to swap the buffer anyway, so it's not too much of a pain.

So on the stern you had to tig on the catch to increase it's height so it would catch the guard bolt?  I don't have the bolt so I'm trying to understand.  Also, the ejector needs to be removed on the stern? Does it interfere?

As I mentioned before, I'm NOT swapping any buffer/springs when going back and forth between my 556 uppers (except the Shrike) and the 9mm Guard.

I don't know your setup and why you need to swap buffers.

As mentioned, this is my link on how I got my setup to work with unmodified Colt mags: http://c3junkie.com/?page_id=597

I think if read that you will get it....

Basically for the 9mm Colt mags and the Stern block were both designed around a straight blowback setup and in those setups the mags are presented higher as there is no barrel extension.
So you have to LOWER the mags for the Guard setup.  You do this by lowering the entire mag block..
When you do that, it is now too low to engage the BHO.

Picture below from my link above shows how the bottom of the BHO tab in the Hahn block was Tig'ed so the BHO tab in the 9mm Colt mag would be able to reach.



The Guard is like a 556 bolt/carrier arrangement.  It relies on the ejector in the bolt (like 556) so you have to remove the ejector in the mag block/lower....
Guard BCG pictured below showing the ejector in the bolt (like 556)


Again, if using the Endomags, you just put in the order notes that this is for the CMMG Guard and they remove the ejector from their Endomag and you just change uppers and mags and done.  I don't change any buffers/springs.

oh, duh, it makes perfect sense now.  I totally forgot how the Guard works.  I was stuck in 9mm blowback mindset.  Thanks for clarifying that, I really appreciate it!  So, was all the work worth it?  Does the Guard on a select fire gun shoot better than a tuned blowback gun?

It is absolutely worth it to me.  
There was some work involved to get the Guard system to work with unmodified Colt mags as I posted above but there is NO work involved if using Endomags.  So not sure what you mean there.

Unless you are referring to the work I did in tuning, tuning is fun for me and I've still got another tweak I'm working on but for now, I've already posted links to the tuning I've done.
I know several people that are using what I've stumbled on with the same success which is:
1. A5 buffer tube (or equivalent like the PSA PA10 tube)
2. 556 Tubb buffer spring
3. 9mm Blitzkrieg/Kynshot buffer (same length compressed as an A5 buffer)
Again, above config happens to be what I'm using for my 556 setup as well now so zero changes when swapping from 9mm to 556 other than changing from standard 556 mags to the Endomags.
I am getting 622 RPM with the 9mm Guard using Endomags as seen in my pic below.  I can easily pull singles with this setup.


I think your second question is already answered if you go back and read all the posts in this thread.  However to expand on this, I had been heavy into SMG competitions back around 2003 through 2006.  Knob Creek has open and closed bolt classes.  For closed bolt, the M16 is what I had and I have tried all kinds of configurations trying to get it to shoot softer and flatter.  The best I could do at the time was an old Olympic Pneumatic buffer which requires a rifle length stock and an LRM integrally suppressed upper...but still a little snappy and have always desired some kind of delayed blowback.

These days PCC shooters running semi auto 'tuned blowback guns' are running heavy buffers with strong springs.  These guns will shoot 'flat' meaning no dot bounce.  The key is using a strong spring and never letting the buffer bottom out so you don't have that bump to your shoulder.  They are also running longer buffers so that they don't have broken bolt catches with that heavy weighted bolt impacting the catch as well as preventing that malfunction where a spent case gets caught between the bolt catch and the bolt.

Both of those (strong spring and extended buffer) are detrimental to my goals as a full auto shooter wanting a slow shooting setup.(desiring RoF in the 600's)
1. Stronger springs increase the RoF
2. Extended buffers reduce the bolt travel which again increases RoF

Both of the above are non-issues for someone with a semi auto.

We all the know the 9mm straight blowback setup is hard on a lower and I had egged out the trigger pin hole slightly on a transferrable SP1 I had running a lot of 9mm blowback and 7.62x39 full auto back in the day.
When I got a RDIAS, I had regulated my 9mm to only RDIAS hosts after that experience.

So while going with a strong spring and extended buffer will get the blowback gun to shoot 'flat' they are not as 'soft shooting' as a delayed blowback setup like the Guard, MPX or MP5.

I have a post sample MPX and MP5K PDW, both are soft and flat shooting but both are too fast and basically NOT tunable.  I cannot easily pull singles with the MPX or MP5K PDW.
I also have the ILWT 4 position gas regulator for the MPX and it is still too fast and it doesn't suppress as well as the MP5 or 9mm Guard.

Which BTW, is another huge advantage the Guard has over all these blowback configurations is how well it suppresses.  I like how both the Guard and MP5 do not have a gas port and so do not rely on the gas system.

If you don't care about how fast it shoots or if you can pull singles out of it in full auto then go with the CMMG recommended configuration of a standard carbine buffer and 308 spring (although I've heard that CMMG is now recommending a standard carbine spring).  It will be softer shooting than any blowback configuration but it will be fast....also note that if you go with that recommendation, you will most likely have bolt bounce issues in 556 full auto as a carbine buffer is too light for full auto 556.

Wow amphibian.  Thanks so much for sharing.

So, what would be the better semi auto 9mm sbr/vraced pistol in terms of sodtwr/flatter shooting: A good mp5 clone (ptr) or a somilar sized guard?

For a semi auto guard, Since it does not have to use heavy buffers what about setting it up to stroke the same distance as a 556 ar15 and with a strong soring to give yourself extra room so the buffer does not bottom out in the receiver ext with your preferred ammo?  I figure either a Tubb 308 spring or 308 round wire carbine spring in an A5 RE w an A5 legnth buffer?

@amphibian

If you read the thread right below this one: https://www.ar15.com/forums/Armory/Full-Auto-CMMG-Guard-Tuning/23-494385/
I've stated that with my latest tuning with the Guard that I personally think the MP5 is slightly softer but I have the Guard shooting flatter than the MP5.  That is just 'my' perception.  Everyone else that has tried my setup side by side an MP5 said they think the Guard is flatter and softer with all my tuning...except for I think maybe one person.

In the thread above, I also mention that 95% or so of my testing has all been unsuppressed. I'm still working on tuning the Guard suppressed.  Rather than dig into all those details again on this thread, just read that thread if you care.

Regarding your last paragraph, I personally wouldn't configure anything with the possibility of having the carrier slam into the lower receiver in the event you forget or someone puts really hot ammo in the gun or whatever.
With the Guard using the 556 Tubb vs 308 Tubb spring, I'm seeing on avg about a 30 RPM increase going to the 308 spring.
I would suspect it will be lot higher going to a round spring.  I have no desire to increase my RoF beyond what I'm doing so can't comment on testing that.  A standard 556 round spring is already beyond what I want so I'm not about to start messing with a 308 round spring.

@amphibian

I did not mean to use a buffer that would allow the actions to open our enough for the gas key to hit the lower receiver. I thought when compressed that 9 mm hydraulic buffer was the same length as an A5

I will continue the conversation in the other thread that you got thit’s all about this

Thanks

interesting!