There are several threads discussing straight blowback etc.. and I think that is already well discussed.  If you think straight blowback is great and anyone that wants something else is just wasting money please don't bother to read on.  

This thread is for people like me that love a locked breech or delayed blowback mechanism for a 9mm PCC or SMG.  

I'm starting this thread here instead of in the 'Pistol Caliber Carbine' / Armory section as I am trying to keep this relevant to the AR-15 family.

I've always been a big fan of the AR15/M16 and enjoying the huge market of aftermarket accessories for it.  

However, I've always been disappointed with the straight blowback 9mm M16.  Always wanted the ergonomics and aftermarket support of the AR15 but the smoothness of the MP5.

IMHO, the CMMG RDB was the first successful attempt to address the issues and as many of you have read, I've done a lot of tinkering with it.
My current status is that I'm running a modified 5.45x39 bolt with 'Dremel' cut angles to control the delay to be as soft as an MP5 and this requires me to run a modified carrier and fixed ejector..(to address the failures of the ejector spring around the 1k mark).

All great but it is a unicorn and I really don't want to have to run custom parts.

I think:
MP5K PDW is smooth
MP5A3 smoother
MP5SD smoothest

I was planning on getting a custom barrel made for the CMMG to do a ported setup like the MP5SD to get the smoothest however paused that since I now see the MEAN Arms roller delayed setup coming out.

I also see the Angstadt MDP-9...but in my mind I equate that to the MP5K PDW.   Sure it will be smooth but you can't tune it and I'm after the smoothest possible setup.
I just don't think you will be able to get it to run as nice as an MP5A3 with that light bolt and short stroke.
Then if you wanted to do an SD version, you have to deal with that proprietary upper and rail.

Now on the MEAN Arms, since only the barrel and BCG are proprietary, it should be no big deal to do an SD version....and by using the a hydraulic buffer and flat spring...i think it would match the MP5A3 or better.

Since it can use a standard upper, I would also think it would be more adaptable to using one of the new Scorpion lowers as well.

In previous posts, I've read that the Scorpion mags are .98" wide.  An MP5 mag is 1" wide.
So use an upper designed for MP5 mags or an AK upper.
 My Polish AK mags are a 1.01" wide.  Using a PSA KS-47 AK upper should also work with a Scorpion lower.

So a MEAN Arms roller delayed upper utilizing Scorpion mags should be easily doable and require probably no mods...may need to trim on mag catch if anything.

I doubt you could adapt the Angstadt MDP-9 to use Scorpion mags with that proprietary upper without some mill work.

I've also posted I want to use a hydraulic buffer and Tubb flat spring which I think would be awesome with the roller delayed action just like it is with the CMMG RDB.

For those that hate the buffer tube, you could chop the carrier and use a Dead Foot Arms kit and shoot it with the stock folded...however, I bet it wouldn't be as smooth as if it was using the buffer tube and a hydraulic.  

So in conclusion, I think the MEAN Arms could do anything the Angstadt MDP-9 could and more.  

Just thinking...dreaming out loud here....what am I missing?

You're pretty much spot on with the points you've made.  I'm personally a big fan of forward, side chargers so the Angstadt is very appealing to me, but exactly as you said, it'll be limited in tunability compared to the MEAN, CMMG RDB, etc.

I was going to mention that too...while I'm not into side chargers, several people have done side charging CMMG RDB setups....so I see no reason why you couldn't do a side charging MEAN Arms upper.  So again, just more options with the MEAN than the Angstadt.....I would also think/hope a lower price point as well...especially when they sell BCG/BBL combos.

ETA:  The Wraith Arms Scorpion lower's matching upper is already a side charger but I guess since it isn't released yet we are not clear on what the mods are required for their side charger.
Also, for the Gibbz side charger.  Posted below is a pic from this thread: https://www.ar15.com/forums/AR-15/9mm-Guard-with-QC10-side-charging-upper/15-728441/ showing how the 'key' is cut for the side charger.  I know you have to use their cam pin but since the bolt doesn't rotate on the MEAN, I would think this would be irrelevant.


MEAN carrier for comparison:  Since it doesn't have a rotating bolt...no cam pin and probably more compatible with other uppers that are designed for straight blowback that may lack the cam pin cut out.


....And if you wanted a forward mounted side charger, I would think you would be able to use the Foxtrot Mike upper with the MEAN BCG.

Be a bit ironic if the CMMG is moar tunable, given you can just cut a new bolt @ different angles - but they need to solve the ejector spring issue, or go to a fixed ejector.

Yeah...was thinking about that too.  My concern there is that I've removed the case hardening on the lugs grinding the angles on them.  I suppose you could try to harden the lugs again.
My 9mm CMMG RDB is down right now as I sent the fixed ejector carrier out to get re-finished and I don't really want to modify another carrier for the fixed ejector yet.
When I get it back, I'm going to slot one of my factory .40SW bolts.  I had a custom SS barrel headspaced with no slop for the angles of the .40SW bolt but it is unreliable with the spring loaded ejector.  I'm pretty confident that it will run with the fixed ejector.  So by slotting the factory CMMG bolt, I should have the hardened lugs and who cares about the slotted area as it shouldn't be contacting anything.

I wonder if the chamber of the Mean Arms upper is going to be grooved like the MP5.

I had my buddy ask them that at Shot and they said yes...don't know if that was just the prototype or planned for production.

All I know is I have put any 9mm projects on hold until the MEAN arms system finally hits the market.

I have various different uppers to build off MEANS bolt and barrel to see which one I think will be the best choice.

Why don’t you try the c-5 lower with MP5 mags?

I was very close to buying a CMMG RDB setup.  The ejector spring issues along with the emergence of the mean arms RDB system has put that on hold.  I'm very much looking forward to it.  I love shooting 9mm on my registered lower, more so than 5.56.

While I do have MP5 mags and think they look great, they don't have last round BHO capability.
I own zero Scorpion mags and would consider buying some for a delayed blow back 9mm build...but I don't want to give up any ambi options I have now.
I really like being able to release AND lock the bolt back from the right side....and keeping it consistent would be nice too.

I'm going to go off on a slight tangent here but again this thread is about what I think the ultimate would be and that would be to have the maximum level of modularity....

I know I'm in the very small minority here but I wish someone would revive the MGI modular lower platform or something that would allow us to change magwells rather than buying new lowers that we may want to SBR and then re-learn where the controls are.  Not only that unless you plan on moving fire control and lower parts around, you have to re-buy all those components to complete the lowers..

https://www.windhamweaponry.com/firearms/rifles/mutli-caliber-systems/ was only selling the 556, AK 7.62x39 and 9mm (Colt pattern).
I have a friend that ordered one of their magwells and it is drop in with the MGI lower.

Some of my magwells for my MGI.


You can see in my picture below that I'm using the MGI lower here and have the ambi PDQ lever above the mag catch.  I still shoot a lot of 5.56 so I love using the same lower for 556 and 9mm and keep my controls consistent.


I think it would do even better today if they were to offer a bunch of different magwell options at reasonable prices.

MGI used to offer Glock small and large frame magwells but they are hard to find these days....I'm not crazy about using Glock mags but a lot of people think that is requirement.  So make Glock magwells for straight blowback and ones with the correct height for the CMMG RDB or MEAN Arms RDB.

MP5 magwell and Scorpion magwells would be great sellers.

Then they could also compete with the Nordic PCC lowers and also sell magwells for the 2011, M&P, and Sig P320.

If MGI or Windham doesn't do it, I think it would be a great opportunity for some manufacturer to do it.

They didn’t give me a round count interval.  I wrote to CMMG about the spring and they sent me more.  I asked how to prevent it / mitigate spring failure and the answer was to remove the ejector and spring to clean out the spring pocket.

That’s not good.  I will toss it into the ultrasonic cleaner and wait for the spring to die (again).

Have you worn out one of the new MK10 ejector springs?...i don't think I've seen anyone post on that yet.   I have about 700 rounds on the new spring in 40SW so far.  I was under the impression that the new spring was supposed to resolve the issue...although I don't believe it.

I have not killed it (yet).  I’m with you, I don’t believe the issue has been resolved.

I found this interview of Mean Arms on Ghost Tactical's show.
https://youtu.be/ovqpeyRP4M0?t=3281

Roller delayed talk starts at 54:40 and goes for about 10 minutes.
At about 1:11:45 they talk about needing a custom charging handle (that's included in the bundle) due to a special cut to accommodate the carrier.
At about 1:23:15 they mention that the roller delay system will be coming to other calibers after the initial 9mm release.

It's nice to know that you could make a custom barrel with their special barrel extension.
I'm sure some folks will be disappointed that it won't work with side-charging uppers, but I don't really care about that anyway.
Also cool to hear talk about .40S&W and .45ACP even though I'm only interested in 9mm.
I do think this would be killer if the EndoMag worked in USGI mags.

Thanks for posting that.  I haven't seen it.  I'm betting it will still work with some side charger designs...just may need to do some mods instead of being drop in.
Shame they didn't discuss if the production version was going to have a fluted chamber like their prototypes and no idea on price yet...

Here's another clip from a few weeks ago:
https://youtu.be/046ChsBeZ5s?t=1232

Rolled delayed stuff starts at 20:32.
Not too much new in this one, they do mention that the complete built upper groups will be available first as 16" and 10.5" (around the 24:25 mark).
Bundles for DIYers will be coming in late summer/early fall.
No mention of twist rate or whether the chamber will be fluted.

Endo Mag fits in GI mags front to back & side to side, but sticks out the bottom.  You could try chopping off some of the bottoms bits to see if you can get it to fit.  I shipped a couple of donated Endos and some pre-ban 30 rnd aluminums to Massachusetts last year, might ask around the MA HTF to see if he ever got it working.

I really hope it'll work with existing receivers like Quarter Circle 10 glock lowers. I have one SBRed.

I think worst case scenario you may have to grind on the mag catch to lower the feed height.

I realize that we don't have much information on this setup yet but from what has been shown, can anyone tell if this would work with an RLL? I have the CMMG RDB bolt and carrier but may go this way instead, if it's an option.

I am a bit puzzled by this line of comments.  M.G.I. is still in business selling their modular system.  Admittedly, perhaps not with as wide a variety of offerings or economical pricing as may be desired by some.
https://www.mgi-military.com/store/index.php?category=21
Their modular system may be patented; which if it is, would require them manufacturing or licensing the technology.

Also, with respect to smoothing out recoil on the AR platform, and still staying on the M.G.I. site, a few years back their Rate Reducing Buffer:
https://www.mgi-military.com/store/index.php?product_id=8&type=&category=7 was considered by some to be the ultimate in recoil as well as ROF reduction.  I've seen nary a word - good, bad or indifferent - about that product in many moons.

Have you tried to buy anything from them lately?  Several people have contacted me offline that they can't get anything out of them.  I don't need anything from them for the past few years so I can't say I have any direct experience with them lately.

I know you're good at digging up patents...have you found one for their lower?  I couldn't find a patent but it was several years ago when I checked.

Yes, I have several of their buffers.  They are heavy and they are great for some scenarios but I don't use that buffer anymore.  I prefer the hydraulics for just about all applications nowadays.

MGI's website is still advertising the Black Friday 2017 sale. Their Twitter account has been silent since Nov 2017. Their Facebook page link doesn't work (says it's been removed).

I'm pretty sure the HYDRA is covered by this patent that dates back to M.G.I.'s pre-Freedom Group days as Bushmaster:
https://pdfpiw.uspto.gov/.piw?PageNum=0&docid=07810271&IDKey=E5EC3018CB86%0D%0A&HomeUrl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D7810271.PN.%2526OS%3DPN%2F7810271%2526RS%3DPN%2F7810271

What is murky to me is who currently has the manufacturing rights.

I've never bought any of their products.

I recently bought a hydraulic buffer, and am waiting for the weather to get warm enough to compare it with an H3 and a 9mm mechanical buffer.

As for the MEAN Arms inclined plane with rollers, lost motion delay product; I am open to considering it but their pricing will be a big factor for me.

Wait...aren't you the one that posted this: If MEAN doesn't feel that M16s are worth a mention, then I guess I don't mean that much to them, and they really do not want me as a customer.

I don't know...I've never seen a patent referenced on the MGI site for their lower....I know they (Mack Gwinn) has several patents...one on their buffer....etc..

The link you referenced does mention Cobb and I thought the Cobb modular lower came out after the MGI.   The Cobb modular lower also has a shelf just like what is depicted in the patent drawings in that link.

Regardless..back to my point, I just wish someone would get busy with a modular lower that everyone could afford and leverage all the current mag options.

Looking at the rendering below...I think you would have to get someone to TIG some material to trip the RLL at the right spot.

Yes, that was me.  Thank you for asking.  I still feel that MEAN Arms was rather terse and vague in their initial announcement. I now open to considering their product(s) depending on performance and pricing.

MHO, YMMV, etc. and be well.

Actually, that rearmost upside down 'U' looks like it might be in the right spot to trip a link but that forward one would get in the way.  Might be as easy as machining it off?  I assume that forward U is in the correct spot to trip a sear.