I have a friend running a Guard with an UNmodifed PSA Glock lower and he is using the same buffer/spring and buffer tube combo I discussed above and he is very happy and says his is running 100%.  He is also running his with a RDIAS in full auto.

I just found out about the Guard. It seems like this might be the ticket for folks that have a lightning link and don’t want to run a blowback upper for fear that the added stress might damage the link. Does anyone know if this system can be made to work with a link?

I competed at the Ohio Subgun match this past weekend with the Guard System in 9mm.  I finished 1st in the Unlimited Division and second in Optics.  Thankful for a good day of shooting with good friends and no malfunctions.  There were some very good shooters there that day and several of them had gear issues or mistakes that they don't typically make.  I've def had those things go wrong and more, so happy for a good day.

In the lead up to the event I noted a few things and made some changes:
- Changed my ejector spring to the Tubbs, but continued to occasional have malfunctions due to rounds not being fully ejected, maybe once every 4 or 5 mags
- Switched from rifle kynshot to 9mm kynshot with A5/.308 length buffer tube (zero malfunctions during competition, so fixed the above)
- this did up my rate of fire a bit and so I plan to play with the rifle buffer with a suppressor, but the 9mm/A5 is currently the sweet spot (using Tubbs buffer spring as well)
- I believe there is still some space to tune this system a bit, but when running weak ammo I did get some malfunctions again.
- When doing extra work to dial in my zero before the event, I wasn't happy with my groups...they were "okay"

For context I typically shoot an MP5 in competition and my groupings with 9mm 124 gr Prime Ammo are maybe 2" at 50 yards (benched)

So perhaps I"m spoiled but I could only get about a 5" grouping at 50 yards with the guard system (and the groups are prone to flyers)

I'm not sure if this is a barrel quality issue or if I need to find some 115 or 147 quality ammo to try, or if its just the way the system unlocks that disturbs the grouping

I did this seated shooting off a bag on the bench at the range, I will try prone in the future.

Also
Big thanks to Amphibian for all his work over the years on these systems and all the other contributions on this thread and others to help us learn.

And - I plan to get this running in 9mm and .45 with my lightning link and believe this is the system to do it with.

I believe that M60Joe is still on vacation, he's done my work in the past.  If anyone has recommendations for other people that can do that work - please let us know.

I'm not getting very tight groups out of the .45ACP using Federal 230 gr, but to be fair it was just the first break-in, sight-in session.

The brass is very sooty and I had one FTE in about 80 rounds. The LRBHO has been working well so far. I'll keep working it to see if the groups come down.

My Guard barrel and bolt arrived today. I hope to assemble my upper tonight and try it out on my QC10 Glock lower for a feed/function test sometime this week.

Did you buy yours right from CMMG?

I did. Ordered last week and was told barrels were on backorder for 4-6 weeks but then got a shipping notice a few days later.

Shot one for the first time the other day, it is super fun!

No problem!

Doctor_Evil, are you still using a carrier weight?
I had removed mine and of course my RoF has gone up...
ROF with 556 Tubbs spring 702 RPM
ROF with 300 BLK Tubbs spring 674 RPM

However, I'm still able to pull singles with either spring.
I thought I was going to settle on the 300BLK Tubbs springs but on a fully loaded mag, it won't sometimes isn't strong enough to strip rounds off.
This is again w/ the Blitzkrieg/Kynshot hydraulic and A5 tube.

I may try putting the carrier weight back in and try the 300BLK Tubbs spring again (I got the 300BLK spring after I removed the carrier weight), maybe with the extra weight it can reliably strip rounds off....as well as dropping RoF of course.

Cool!

I ran about 50 rounds through my Guard upper yesterday.

Specs:
-CMMG Guard 8" barrel and bolt
-Milspec upper (I found that the bolt would not go home on my QC10 pistol MUR upper)
-Standard carbine spring and KAC SR-15 buffer (listed as a hair lighter than a standard carbine buffer. I grabbed it as it was readily available though I'd like to try some other buffers)
-Old/early model QC10 GSF lower (I did remove the ejector and little feed ramp from the lower as they were in the way of the bolt)
-Geissele SDC
-Liberty Mystic X and SiCo Omega 9k suppressors

Overall thoughts:

Out of the 50 rounds I had a small number of malfunctions. I'd estimate an 85-90% success rate and all I wanted to do was quickly test the platform before going further down this road. A few times the BHO would engage mid magazine which was a little odd. The other malfunction was an occasional stovepipe or I guess failure to eject. Mags cannot be inserted on a closed bolt which isn't a big deal. The setup did seem to get a little more reliable as the I put some more rounds through it. The Mystic X seemed a little more reliable (maybe more backpressure?) than the Omega 9K but hard to tell with such few rounds downrange that I don't know if any real conclusions can be drawn. Ultimately I want the Omega 9K to be on this setup but I wanted to be quieter for the time being.

So far I'm happy and optimistic about where this project is going. I've got some more tweaking to do but I like the "proof of concept" experience yesterday. Going from a 12oz buffer in my old blowback setup to a 3 oz buffer and shaving weight in the bolt makes a far more pleasant shooting experience. I'll get some numbers here soon on how much weight was shaved by swapping to the Guard setup. Ideally I'd like to get the barrel down to a 5" range with a 3 lug setup for the can. I'll play around with a few buffer weights and would like to try a JP Silent Capture spring. I also like that it seems there are more trigger options with this setup that are less likely to get beat to hell compared to blowback builds. I was using a ALG ACT but it feels good to get a 2 stage back in.

I'll be gearing up to sell all my old blowback build parts and pursue the Guard build full blown.

I use KCI 26rd mags and have zero issues. I orginally bought two because I saw some bad reviews. The two I had function fine with several different types of ammo so I bought 4 more. They were used in a New Frontier Armory AR45.

Gunmag Warehouse - KCI "Glock" 26rd

Ha ha...always one step ahead of me!  I was just wondering about the low power spring!  I have one, but I've also heard that the .308, regular Ar-15 and the low power are all the same spring with more or less coils....so it could probably be tuned a bit.

I had been using the Kynshot rifle buffer and the 1oz weight (smallest one) and I was getting well below 600 RPM, was so nice to basically shoot it almost like it was in the semi-position.
But because I was getting a malfunction every 4 or 5 mags, I knew it wasn't good enough for competition.  Especially since those malfunctions are UGLY...the case gets jammed into the bold sideways and it has to be pried out....no standard malfunction clearing procedure works for that!

So I dropped the weight when I went to the 9mm.  ROF def went up...can get singles when trying harder..but competition was def a mixture of lots of singles and doubles.  But I had absolutely 0 malfunctions and LRBHO worked every single time.  I'm hoping the wight will help.

Maybe we can add the weight (1oz)..which by the way still allows you to use a LAW folding stock adapter! and trim a coil or two off the regular power spring?

It is also worth mentioning that (maybe I did before) that was 100% reliable with hot ammo.  When I ran some really weak gammer ammo....it ran super soft and smooth, but I did get a few malfunctions.

I apologize if this has been covered before but I was trying to avoid reading 11 pages...

Can the Guard barrel/bolt be used in conjunction with the grease gun mag fed lowers ?

Thanks

I have a buddy using a Bazooka Brothers GG lower with the 45 Guard with no issues. That lower requires to mod the GG mags anyways so he just modified the mags to work with the appropriate height required for the Guard system.

I always thought running a RDIAS was a no go in these 9mm only lowers?

Why it's an AR?  It takes standard safety and FCG.  Only the magwell is different.  But anyway I am in the process of switching over to a MGI/Windham system and will use standard Colt type mags or better yet the new MEAN adapter system if it sees the light of day.

That’s awesome.  The next question I would ask is, does the radial blowback design solve the issue of broken hammer/trigger pins and egging out lowers?

Absolutely.

I don't have as many rounds downrange as amphibian but the RDB is far less brutal on your FCG vs direct blowback. I don't see any issue running whatever FCG you want with the Guard.

Glad I found this thread since I'm shopping for a CMMG 9mm complete build that will work out of the box with my RDIAS.  (not including FA FCG,Selector)  I looked at the .45 and that is also an appealing option.  Lots of good info in here to peruse.  Have been corresponding with Bryan at CMMG Tech Support already but want to read up on personal experiences before I load up on more gear.

Btw the folks at CMMG will get my business.  Their website "About" page says a lot about the way they approach business and I like the way they put their faith up front.  Bryan has been swift to respond to my many questions to boot.

I'm still interested in using my existing SBR stamped Spikes ST-15 lower with the Guard RDB 9mm upper and a mag well adapter (RDIAS) if it has been shown to make a reliable combo.  Brian at CMMG said they use a standard carbine buffer with a .308 carbine buffer spring in the 9 mm Guard so I may be gtg there but he also said someone had tried using a AR-15 mag well adapter and the Guard RDB upper with poor results.

I reviewed your tests and you have quite a bit of time hands on with the RDB setup.  Good stuff there.  Can you or anyone else in here give me some real world experience with the Guard RDB upper on a AR-15 lower?  I'm not knowledgeable enough to feel comfy experimenting.  Hopefully someone has had success by now.

Here's a review of the Guard from a couple weeks ago.  Nothing new I don't think but a good current review and includes an illustration of how the RDB works.
Guard Review August 11, 2018

Have you looked at this thread? https://www.ar15.com/forums/ar-15/Anyone-seen-this-MEAN-Arms-9mm-adpater-/15-728601/&page=3
I've modified my 9mm Hahn block to work with unmodified Colt mags here: http://c3junkie.com/?page_id=597
But as discussed in the first, link, I'll use the Endomags if they have less resistance stripping rounds than the Colt mags.

Holy Smoked Barrel!!  That MEAN Endomag looks like the cleanest solution with all the extra 30 round magazines I have.  Very ingenious!  Second video after the first mentions Guard compatibility to boot.  Cool thing is it matters not which BCG you have, works with them all.

So I should be gtg with the CMMG RDB 9 mm upper as long as I have MEAN Endomag or other satisfactory magazine solution?

If so I am ready to do some more biz with CMMG today.

Thanks amphibian!

ps.  Folks in California check this out:  MEAN Loader

Brian at CMMG tells me they have an Endomag in hand but haven't tested yet with the Guard.  In the video it looks like a standard 9mm PCC upper is used.  He mentioned since the Endomag has its own ejector the Guard ejector (on the bolt face) may have to be removed.  Not sure yet.

EDIT:  Tommy at MeanArms says The Endomag can be ordered without the ejector so it can be used with the Guard RDB BCG which has the ejector in the usual place on the bolt face.  Specify when ordering.  They will ship at the end of September I'm told.

You can inform Mean Arms that you will be using the EndoMag with the CMMG RDB system and they will send you an EndoMag without an ejector.

Right.  This is already discussed on page 3 of this thread: https://www.ar15.com/forums/AR-15/Anyone-seen-this-MEAN-Arms-9mm-adpater-/15-728601/?page=3
I've already corresponded with Mean about this.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Link Posted: 8/21/2018 7:39:14 AM EDT ReportDiscussion ForumsJump to Quoted PostQuote History
Quoted:
I also contacted them regarding the Guard wondering if the ejector could be put back or is it a permanent change. They replied that it has to be cut off so no putting back.
I also asked if they is any other mod like mag height and waiting for a response.
I got a response back that the mag height is NOT altered for the Guard....so just cutting off of the ejector. That is pretty awesome, so you should be able to use a standard, unmodified AR mag catch with the Endomag and it is just an upper swap to go back and forth from 556 to 9mm....(Yeah, I know they did that in the video but I was skeptical that either the Endomag's insert's height was different to accommodate the Guard or the mag catch was altered).

I already ordered a few.  Sounds like a lot of issues I've been investigating have been solved with a combo of the Endomag and the Guard RDB BCG.

How do you like the response time from Tommy Lawson at Mean?  Swifty.  Brian at CMMG is quick on the reply emails too.  Sounds like a great combo so we can all have more gear and fewer quirks.

Curious if anyone has tried to use the Guard BCG/bbl with a pistol-caliber side charger like NFA/Spartan makes. I guess I never even thought about cam pin on the guard vs. blowback. I'd really like to use the existing side-charger even if I have to mill out the ejection port more. I think if I dropped another $200+ on a side-charging 556 upper the wife might kill me.

My thought was I'd have to buy a modified cam-pin from the 556 style upper and open ejection port (even more), but I read somewhere there might not even be a provision for a cam pin in this style of upper? Thanks all.

Does anyone know what mag block this guy is using to get the CMMG upper to run with Colt mags?

https://youtu.be/e8D1ZzE2Ydo

https://youtu.be/FxUcRN31hy4

No comments below the video and no way to tell.  However it makes me more comfortable about buying Endomags to use with the Guard upper.  Don't really want to mess with blocks or mags I don't already have.

Someone asked in comments on the second video where the owner had to Dremel to get his RDIAS to fit.  I am assuming the rear lug in the 9mm Guard upper has same dimensions as the standard AR-15 lug but I could be wrong since I don't have the Guard upper yet.  I had to shave a couple thousandths (a bit front side and back side) off the rear lug of both my uppers to get my RDIAS to fit.

Guard thread / amphibian video
Video below of amphibian running his RDIAS in the Guard.  He said he was using a modded Colt mag block with un-modded Colt magazines.

Those videos are from member badkarmaiii. I believe he was using an AMM magblock.

https://www.ar15.com/forums/industry/9mm-Guard-Barrel-and-BCG-working-with-Colt-mags/145-286362/

Clutch, big thank you!

@CMMG

Sorry if I missed it elsewhere in the thread but do you still plan on coming out with shorter barrel lengths?  Was hoping for a ~5" guard barrel/bolt combo.

You mean like the Banshee?  It also uses the RDB system.  That is the one I have an eye on to use with my sbr stamp and rdias.
Banshee

I've been waiting for a response to the same question.  I wish they'd release the banshee bolt/barrel combo.

You don't want a Banshee upper?  I must be missing something.

Yep for those not wanting a complete Guard upper, CMMG sells a "builder kit" (barrel, bolt, & carrier):



They currently only sell them with 16" & 8" barrels so others like me are waiting for the release of shorter ones like those on the Banshee.  Haven't been able to get an answer on when that might happen though  

I bought the 8” and sent to Adco for a chop. Hate that I had to do it that way but I didn’t want to wait for a shorter option.

Ah, I get it.  I have a question for Brian about their 22lr conversion kit so I'll ask about the 5" barrel builder kit too.   He has given me an answer to every question I've asked by the next day so far.

How many folks would you say are waiting for that option?

Oh man, hard to say.  10?  10000?  Reading through other threads, posts, etc I know there's a handful of folks who've mentioned the desire to see shorter barrels.  So who knows; for everyone who says something there might be 100 more thinking the same thing.

I could see CMMG's reluctance to make a special length like 4.5" or 6" since it means programming, CNC time, etc.  But 5" is easy since they're already making them for the Banshee.  My guess is Brian will say "eventually" for the 5" option because right now all of them are going toward building complete guns & uppers.  (Or something like that)  Keep us posted!

I would have but I bought an 8" and will have it custom chopped.

Same here.  Bought the 45 and 9mm and sent both to Morgan at Class 3 Machining.

I have another Guard build in the future so that one (hopefully) can wait for a factory 5" barrel.

You were right on the money.  It is going to be a while according to Brian at CMMG:

"Unfortunately, we can barely keep up with those as it is… all of our 5” barrels are currently going into BANSHEE builds, as they’re selling faster than we can build them.  So, for now, we cannot delegate any to retail sales and won’t be able to do so until production on the BANSHEE slows down.  So, it may be a while.  All of our barrels are turned here, in-house."

The 5.7 Banshee is a blast!

I have an sbr'd PS90 with a Sparrow on it.  At the range one day a friend called it a "pea shooter".  Is the 5.7 x 28 on a come back trail or was it never really fading away?

Never really fading as far as I know, some fudds call a 5.56 a pea shooter too.

P90's really shine in full auto, but the amount of rounds you can get on target in a hurry make it viable even if people post 22mag gel tests in comparison.

I missed that so at least there is some kind of option.  But an extra $300+ for stuff I'd just get rid of anyways?  Eh.  I'll just keep shooting what I've got and wait for the short barrel/bcg combo.

I wonder how much softer these actually shoot compared to a 9mm SBR that's already been tuned to shoot soft.  Mine is pretty soft as is.  Wonder how noticeable the difference would actually be.

Haha!

I figured as much since I got a similar answer last year shortly after the Guard debuted and they mentioned the builder kits.  In the end I think it was ~8 months before they hit the shelves.