I think I’ve done a pretty decent job of laying out just how not modular an MP5 is compared to newer market offerings.

Pardon my ignorance, but is there a reason that more AR9s aren't gas operated as opposed to blowback?

9mm is too dirty to run reliably for long in a DI gun.

Not enough pressure.  
I used to have a gas operated 45 by RMW.  Macon Armory also does them.
Both require the gas port to be really close to the chamber.
Both work quite well.

RMW did/does gas operated 9mm as well but it requires you to use handloaded ammo with specific clean burning powder.  Friend of mine has one and he handloads for it but even then, he can't make it through a full auto sub gun match before having to clean it.

I also have a full auto Sig MPX which is piston operated and thought this would be the answer to my prayers for something to finally compete with the MP5.  I dumped a bunch of money in mags, 4 position gas regulator by ILWT, ILWT 3 lug barrel, stock etc.. running full auto with a post sample drop in sear.  
While smooth suppression sucks with a muzzle can with the MPX.  It is gassy and loud.

While the MPX does have good ergonomics, I highly value suppression and so still rate the MP5 higher.

Now that the CMMG Guard/Banshee is out, I think it is best currently available.  Even better ergonomics than the MPX since the Guard can take Endomags and standard lowers and ambi bolt hold open and release options and tunable since you can use so many different buffer/tube and spring options.

I really like the standard AR gas system but only for rifle calibers.  After my experience with the gas operated pistol calibers, I would just rather a pistol caliber to not use a gas port at all.  I'd rather not worry about burn rates for pistol caliber and how clean the powder is.

For pistol calibers, I prefer mechanisms that delay the cycling by some mechanical method like rollers (MP5) or the Guard (angles on bolt lugs).

I don't know which newer market offering you are referring to but as I've posted several times, nothing can touch the modularity of the AR platform.  On page 2, I posted 10 FACTS why the CMMG Guard is better than the MP5.  
(However, I still like the MP5, it is a PROVEN CLASSIC).  I know the CMMG is not proven at all and I don't care as I just use it for competition/training.

With the CMMG, I think it is amazing that just a BCG and barrel change and specific buffer/tube/spring selection and now we are in MP5 smoothness territory.
It was my tinkering with it that I stumbled on that buffer/tube/spring selection which works great for my full auto 556 configurations and now I just do straight upper swap between 556/9mm.

The great thing is that the market is still aggressive in the AR world and new buffer/spring/ tubes/actions are always coming out so you can mix and match to whatever you desire.  You cannot say the same for any other platform.

Lot of people rave about the BT which is straight blowback but also has a hydraulic buffer.
With the AR platform, Kynshot makes several different hydraulic buffers to choose from with varying dampening and weights.  Using a hydraulic buffer and a delayed blowback action results in a way smoother action that closely rivals the MP5 and surpasses every straight blowback offering on the market today (including the BT)....and we are not talking a lot of money here.

I don't know why everyone keeps acting like it is.
Again, if you go with a straight blowback AR9, you still have to use heavy buffers/springs and certain aftermarket triggers are not supported to be used in blowback AR's (like Geissele).

I would argue that you are spending more on a straight blowback AR9 since you will most likely dedicate a lower to it due to the specific lower parts to run that blowback upper.  I'm sure someone will dig up some super cheap straight blowback AR9 options to argue a point but again, if you run a Geissele and some other match triggers, they are not supported in those straight blowback setups.  So now you are not keeping things consistent.  
Also it isn't just about money but convenience, I'm at the point in my life where I don't want a lot of different platforms and calibers anymore.  I still have several different platforms but most are toys and I don't train with them.  I train with the AR the most and want my lower configuration the same no matter what upper I put on it for anything serious or competition.

I know a lot of you will be like who cares about consistency and convenience.  Well I do and I spend the time posting this kind of information for those that are are like me that do appreciate having these capabilities.

bolt catch is on the wrong side!
BAD lever? cant bring myself to do it.
Radian system? sure! but its not a lightweight.
the bolt catch is not a big negative to me really but still a negative.

i also dont hate the rear charging handle i just see it a small negative. blowback vs delayed might be a bigger negative but nowhere near a deal breaker for me.

Thank you for the detailed answer, I figured it had to be something like this.

I concur on the BAD lever.  I dont want anything in my trigger guard other than a trigger.
I like the PDQ.  As pictured below.  I can lock the bolt back and release it on the right side with my index finger.
Same goes for the charging handle, dont like it?  There are products to go with a side charger.
All your negatives, can be resolved with off the shelf products.  Also, if you start with just the BCG/BBL combo and not a complete gun, you are not double buying and you will end up with exactly what you want.  Only the AR platform offers this level of versatility.  So I dont think you can call it a negative if you just get the BCG/BBL combo 1st then whatever ambi option and side charger you want to complete the build.
Now if CMMG forced you to buy a complete gun or complete upper I would agree but thank God they offer the BCG/barrel seperately.

Yeah, the only thing I would like with the Banshee (wanting the smaller frame) is using a different magazine vice Glock.  There's no reason for it as Glock mags have proven reliable in PCCs, but it's not something I prefer.  However, that said, I have a dozen 33rd Glock mags...The Banshee would be the logical choice for many reasons.  Ironically, I picked up the cheap ATI AR15 9mm "pistol" which takes Glock mags and it has been surprisingly reliable; zero issues.  No bolt hold open which sucks, but it's like a cheap AK version of my PCCs, I toss it around, abuse it, rarely clean it and it just keeps plugging away (but it's also essentially an AR9).

ROCK6

I really want PoF to get back to the PSG. AR controls, no recoil spring in buffer tube (could use folding tubes or MCX-style rail+hinge stocks), locked breech action

Where do you see locked breech?
The animation just looks like a light (violent) blowback bolt, but with an added gas vent near the chamber for whatever reason.

+1.  I remember seeing that animation now.  Not enough details to know how it works.
I guess I'm biased but after my bad experience with the Sig MPX as well as my friends experience with his gas operated 9mm, I don't want a 9mm SMG that has any mechanism that has a barrel with a gas port in it.  Figure out some way to delay the cycling without tapping any gas is what I personally prefer.

Right. It is just blowback. That animation even shows the issues compared to delayed... Good example for this thread. That action was moving and the pressure is clearly high while the bolt opens.

https://www.youtube.com/watch?time_continue=68&v=uNqXFjQyZDY

I can give you another reason to skip Glock mags. They're at the wrong angle. They're canted past 90º, where Colt and 556 mags are 90º and MP5 / EVO / curved mags all insert and lock before 90º.

It's not a problem in a handgun. But consider if you have a Glock mag PCC that you need to insert the new mag at the "wrong" angle. You need to start closer to your body and push away, or angle the gun out to the strong side just to get back to 90º. I don't think it's a small thing personally. I'm looking at it from terms of competition (USPSA PCC) use and I'm definitely faster loading 556 sized/angled mags than guys with Glock mag PCCs. I think it's because of the awkward angle.

Again, not an issue in handgun because you're lining up hand directly to hand, which I'm convinced is always faster than hand to extension from hand. Maybe I'm wrong on this.

It is DI of some sort, iirc

I agree, new21022. I've handled a number of Glock mag ARs and they just feel "wrong".
I'm sure that could probably be trained out of me, but I'll just be the luddite of the group and struggle along with my antiquated Colt SMG mags... and blowback actions.

I usually stay far away from these discussions, BUT.....

I agree with amphibian (and others) that the CMMG RDB system is the most significant advancement in delayed blowback systems since the MP-5, but I still find it unnecessarily expensive, at least in comparison.
The telling comparison most here would make is $330 to $350 for a RDB BCG and barrel from CMMG as opposed to $299 - $319 for a complete 9mm upper from PSA including BCG. That's what they have to compete with (arguments about quality differential aside).

And I get it. It's a night and day difference from the MP-5 A2 I was trained on (or even the open bolt UZIs of the same era) to the blowback AR-9s I own now. But at the end of the day I think that you currently have to be someone who is WAY into either the technical minutia of the system and/or equally into the performance advantages that system provides to make it worth it.
What can I say; we all like (1) cheap stuff that (2) works, and easily tunable blowback actions provide these two things.
However....
I very much hope the RDB system gains real traction, and if CMMG licenses the design (I'm looking at you, PSA) and prices drop precipitously (and someone makes a Colt SMG mag lower to address the "deck height" issue w/o mods), I'm in!
Oh who am I kidding; I'll probably be in anyway. I'm a technical minutia kind of guy.

I absolutely love shooting my Evo K but that being said it’s not in the same league as my MP5 ( Zenith )

I’ve also owned a Gen 2 MPX I stress owned I hated that thing

Hopefully, the animation is wrong but it appears to be:
1.  not locked breach
2.  vents gas right by the gas port (like an MPX).

My MPX sucks as a suppressor host being gassy and loud due to venting gas at the gas block.  If they make it like the animation shows, I would anticipate it to be loud like the MPX.

Thanks for taking the time to post.  I appreciate hearing from you guys with real experience behind full auto MP5's and open bolt full auto UZI's.

I totally agree that $350 for the RDB barrel / BCG is relatively high compared to a straight blowback combo but:
1.  CMMG deserves a premium for their R&D.  If it was a product that could be imported into the US from China, it would be ripped off and sold cheap.  I am willing to help support innovative new gun products.
2.  I think you are overlooking the required components in the lower to run a straight blowback.  So it isn't just the upper we are talking about.  I know you 'can' do a straight upper swap of a 556 upper and slap a cheap PSA upper on top...but you would need a mag block or run Endomags for straight blowbacks (which again have the ejector in the mag now and you have to leave mag in the gun to clear).  Then you need to run a stronger spring and much heavier buffer and/or longer buffer or put quarters in your buffer tube to keep from snapping your BHO from the increased distance & force of all that mass when the BHO engages after the last fired round.
Adding in the heavier springs, different buffer than you run in 556, mag block or Endomags = more $$ than the RDB BCG/barrel combo.
3.  Again as mentioned before, Geissele doesn't support any of their triggers to be used in a straight blowback AR.  CMC and others make triggers specifically designed for straight blowback.  So if/when you decide you want to upgrade to a nicer trigger, you have to double buy triggers instead of using the same trigger you would use for 556.

So are you really saving any money?

4.  Lastly, Time / Convenience / Consistency - I can't put a dollar amount on those 3 things.  It varies for everyone.  I don't have time like I did in the past.  I don't want to be swapping parts when swapping calibers.  Some will say it's so 'cheap' (which again I would argue based on #2 above) to just get a straight blowback gun and just switch to a whole gun rather than swapping uppers.  
That comes down to convenience.  When I go to the range, I already have a bunch of things to bring, one less gun to bring means more ammo I can bring.  Consistency, as mentioned I'm an AR fan and love the controls and modularity.  Going to a straight blowback AR will not give me the consistency I'm looking for in regards to the trigger in the lower and the magazines using the RDB Endomags aka licensed CMMG ARC mags.

Time/Convenience/Consistency are very important to me.  
The CMMG RDB design helps me with all that along with:

• superior suppression to a straight blowback or Sig MPX for that matter
• a recoil impulse inline with the MPX and MP5
• more modularity and parts compatibility than anything else, I can't stress this point enough.  This is basically future proofing this platform.  Only with the AR platform do you have hundreds of manufacturers making parts for it.

All that said, while I'm grateful that CMMG does sell the BCG/Barrel separately, I wish they would sell other individual parts separately like the carriers, bolts, cam pins, ejector springs etc...although I did have them replace a couple ejector springs at no charge, I would like spares.  Maybe they are just stingy with the parts to keep up with demand..I don't know.

I don't think you're wrong, but it's not as intuitive as a straight insert.  I'm sure training could overcome the angle, but it's something I would like to avoid.  Does anyone know if CMMG's upper would work on a Spikes lower designed for Colt Mags?  I would like to have the RDB upper with a Colt mag lower, but I think the ejector might be the issue?

ROCK6

I've documented how to use unmodified Colt mags w/ the Guard system here: http://c3junkie.com/?page_id=597
You would have to do similar mods to the Spike's lower.
Yes, you would have to removed the fixed ejector in the lower.  Also note that doing this method, would allow the mag to go up if you used the mag for a monopod (which I personally don't do).  
You could also make a new notch in UZI mags that matches a modified mag catch to eliminate any up/down play.

However,  I'm curious why you don't want to just use the Endomags for the CMMG RDB setup?  You would then just use Gen 2/3 Pmags and have the same exact motion inserting those mags as you would with 556...also use the same pouches.

Thanks for the mods!  No desire to use Endomags; just personal preference but I acknowledge their value for training and using the same gear.

ROCK6

To your point about spare parts, i actually saw some for sale on opticsplanet the other week. They had complete bolts, carriers, bolt rebuild kits, etc.

Love reading your posts btw. Really enjoying my RDB setups.

ETA: https://www.opticsplanet.com/cmmg-inc-mkg-mkgs-complete-bcg-repair-parts-kit.html

I know they had other stuff too like carriers because i remember looking at all of them but opticsplanet's search engine sucks so that's all i could find for now.

Thanks!  I had no idea CMMG was releasing those parts!  They need to sell the .40SW bolt separately for 100% suppressed build rather than throw weights in the carrier.

And thanks for posting back!

To your points:

1. No argument. I absolutely agree.

2. True. But only of you're actually converting an existing 5.56mm gun or wish to switch back and forth between calibers, in which case the RDB upper and endomags are a godsend. However both of my current AR-9s I built from the beginning to be dedicated 9mms, so no wasted 5.56mm parts or swapping springs, buffers, spacers etc. But good point for anyone not starting from zero as I did.

3. That will continue to be an issue for the simple reason that there is no single spec. for blowback BCGs. Unlike 5.56mm carriers, everybody seems to have their own design or a variation thereof of the original Colt's bolt. Personally, I stayed with mil-spec triggers on my guns for the simple reason that these are firearms that would most likely be used at defensive ranges and situations, and a sub-3 pound trigger would actually have the potential to be a detriment when the old adrenaline starts flowing. But for a competition gun it's a different story.

4. In your situation I could see that. I'm more of a "one gun at a time" kind of guy so I rarely bring more than one gun to my range. That way I can concentrate on a single firearm /caliber / magazine type and have less to think about in terms of stuff to remember to take.

The modularity and adaptability of the AR platform and the multitude of parts manufacturers are precisely why I would like to see CMMG license the design to get a higher volume of the RDB guns out there. Parts will then become almost ubiquitous, and of course the system will become cheaper at the entry level. Win Win!

Good conversation and my viewpoints on your responses.
2.  I agree with what you are saying and from my perspective I think 90% of the people that go to a 9mm AR already have a 556 AR.  I would doubt that most people would start off on a 9mm AR.

Point #2 is about money however, for me point #4, Time/Convenience/Consistency AND getting the best performance in smooth/soft shooting and suppression will trump #2 but again that is just me!

The CMMG/Guard has checked all my boxes to achieve my goal of surpassing the MP5 and yes I've dumped a lot of money into the straight blowback parts and accessories starting over a decade ago but willing to dump it all now.  I' believe that for those that build up a straight blowback 9mm AR, no matter what you do, it will never have the softness/smoothness of a delayed action or be as good of a suppressor host (with a muzzle can).

3.  I'm no operator but I am using a Geissele SSF which was made for and used by the "Special Operations Community" as mentioned on the Geissele website.  For those not running full auto the SSA-E is the semi equivalent of the SSF.

4. As mentioned before, I'm all about beating the MP5 w/ AR/M16 controls.  I go into more details on my website on what my criteria is for beating the MP5 here: http://c3junkie.com/?page_id=538

2 or so years ago, if I was able to check all those boxes and have to give up the Time/Convenience/Consistency attributes I would have done so....and I did do that as I was so tired of waiting for something that I went with the Sig MPX as nothing else was out at that time.  Totally disappointed in the MPX for reasons already discussed.

Fast forward to today with the CMMG RDB, I can have my cake and eat it too.  I don't have to give up my Time/Convenience/Consistency attributes and have surpassed the MP5 based on 'MY' criteria on my website.

If something were to come out tomorrow, that has all the AR/M16 controls and meets all my criteria, I would definitely look at it.  However, FOR ME to move away from the CMMG RDB setup would have to be something that is still using my standard AR/M16 lower as now I am spoiled with using the same lower, trigger, ambi PDQ to lock and release the bolt on the right side etc.  I can't see myself going to any other 'closed bolt' 9mm SMG and give that up.  So it would logically have to be a new upper design.  Again something that doesn't have a gas port in the barrel.  Roller delayed blowback upper but still use the buffer tube for using a hyrdraulic buffer or whatever new buffer / spring advancements that come out.
I still think a fixed ejector for a 9mm SMG is the way to go which some of you may know, I have my 9mm CMMG Guards equipped with fixed ejectors now.  However those mods are a one off.
The new ejector design on the .40SW may have resolved the issues I have run into on the 9mm but I have not run it enough yet to determine that.

Now for open bolt, I still love my full auto full size and Mini UZI's but that is another discussion.

Why don’t closed bolt PCC/SMG’s use delayed blow black systems like pistols do, in general? I can see why maybe a tilt barrel mechanism might not work in a 8” barrel but many PCC’s have barrels < 5”. Also there are other mechanisms like falling block.

Simplicity and ease of manufacture.  Hard to put a pound and a half slide on a pistol and still have it manageable.  Easy to do on a subgun.

Lots of race guns with 20oz slides!

The difference isn't that it can't be done in a handgun, imo, it's that no one would accept it. People would HATE a straight blowback handgun when given the option over a locked/delayed design. But because it's cheaper and people accept it, straight blowback in PCC is A-OK.

Thus the entire point of this thread. Once you know the difference, it's not OK anymore (with exceptions).

You also get a stupidly high rate of fire if you take a typical recoil operated (not delayed blowback) pistol action and make it select fire --usually well over 1000rpm-- because of the lighter parts and shorter reciprocating travel.  You can dial that figure down to reasonable levels with heavier parts & longer travel...but you might as well just do simple blowback at the same time & save a bunch of complexity.  Plus, straight blowback allows you to make a gun with no external moving parts, including barrel attachments/silencers.  That's a big plus in close quarters where stuff can get in the way & cause failures if it has to move as part of the cycle.  The TMP/TP9/MP9 does this with a frame-mounted silencer that stays stationary relative to the barrel, but that has some drawbacks of its own (giant attachment mechanism, and gas pressure acts on the crown of the barrel like a muzzle booster so the system is super over-gassed, and unavoidably so)

AKA, Hipoint pistols. :)

Noob comment, but when cleaning my Zenith Z5-RS (MP5 licensed version) I saw the roller delayed mechanism, doesn't seem that complex. Why then are so many companies averse to building a roller delayed blowback and instead releasing a lot of straight blowback guns at premium prices? CZ, B&T, and others included.

It can certainly be done, but cost of manufacturing needs to be taken into account. MP5's while I agree the roller delayed mechanism isn't super complex, it isn't cheap to manufacture the entire gun and needs to be done right for the gun to even work. That's why clones of the MP5 cost damn near $2000. Also, for a more recent example, look at the new LWRC SMG-45. That's delayed blowback, but costs like $3000. People are/were losing their shit over that thing for how much it costs, but you're paying for the R&D, manufacturing costs, etc. Just my two cents

Rightly said. Until those things sell in large masses like the Glocks, the buyers will have pay for the recovering of the R&D, and manufacturing costs.

Discussed many times over the years.  Here is a link to an old thread where High Caliber Conversions MP5, upper on a RR M16 lower.  There was a thread on UZItalk where the guy that built it said it was a major pain to do it.  People begged him to make them and he declined.

There is also the old Calico 9mm that is delayed roller blowback.  I uses a steel cage that the rollers engage in the receiver. I wish someone would do the same thing in an aluminum receiver and make it compatible with all the blowback 9mm AR barrels out there....but for now, I'll have to be content with the CMMG RDB...

Perfectly agree that it is a major pain for an individual enthusiast to build a roller delay cage but for large companies like CZ, B&T, Stribog (I know they have the A3), and, others and even PSA, with the right tooling/dies and their significantly larger budgets it should not be that hard. The only thing that might be stopping them is that they think or have analyzed that  the market is not that big to invest in there.

CMMG though smaller than the above is already there in its own way with its radial delayed blowbacks, and some like LWRC have mil contract over-runs at double the prices, but at least they are moving in the new (already known) direction and not being like B&T and trying to solve a problem that has already been solved by putting expensive hydraulic buffers in a straight blowback.

Let’s see if PSA will have any delayed blowback system in their rumored MP5 clones.

Because bending sheet metal is expensive?  The R&D for roller delayed blowbacks was done in the '60s, surely its paid off by now.  Is it really so difficult to press in a trunion or two and do some welding?  Anyone with the desire and equipment to do it can do so in his garage, hut, or cave.  There are dudes, right this second, machining pretty decent 1911s in the jungle in the Philippines for sale on the local black market.  MP5s and their clones cost what they do because that's what the market will bare and because of supply and demand for demilled kits.  How much do you really think it costs to make an MP5 with Pakistani labor?

Less than $200 per MP5 going by the prevailing wage rates and the infrastructure/machinery already in place.

P90 laughs at you.

Sure the R&D on MP5 roller delayed know-how is already done, but as for actually how to build them? That takes R&D too if you're starting from scratch. And yeah the actual bending of flats isn't expensive or complicated. But all the other stuff you need to do afterwards (and the special tools, jigs that are also needed) is complicated and costs a lot. I can't honestly see an mp5 of all things being that cheap or easy to make compared to something like a Scorpion.
That's two polymer injection molded receiver flats held together by a few screws with no joke, ~17 inch/pounds torque, barrels that do use a trunnion but no drilling and pinning needed, and a big block of steel with some holes in it that serves as a bolt. If anything, I think scorpions are expensive for what they are as opposed to MP5's and clones. And I say that as an owner of both platforms.

If it were really that easy or cheap we'd have had AR15 priced MP5's a long time ago. Sure lots of guys have the desire to build their own but not everyone has the equipment nor more importantly imo, the skill/expertise to do so.

I can see the Pakistani's probably having cheaper labor than others, but POF also have real HK tooling to work with and the license to do so, plus all the advantages those bring (i.e. not having to start from scratch). Perhaps the labor is indeed cheap, but tooling and licensing are not, not to mention in POF's case among other imported clones (and even the real deal HK i guess), we still need to consider importation costs, distribution, excise tax, etc. Companies Still need to turn a profit as well. I can see why even imports cost what they do.

That said, the PSA offering will be interesting if it really does come in at the rumored ~$1k price point, but that remains to be seen. Sure as hell going to be a lot of unpaid beta testers doing some free R&D for them if we're being honest here (recent example: looking at you AKV)

The amount of machining required on the bolt components of the MP5 is probably more than all the machined components put together on a CZ Evo.

The bolt head itself has some broaching and/or EDM, and there are a lot more setups / steps in general.

While all true, it also really just comes down to a roller & wedge, so it doesn't seem like it's a lot of development work if you wanted to pop something in an AR upper.

Don't get me wrong, I'm not engineer, nor did I stay at a holiday inn, but it'd be interesting to see a wedge & roller setup that was small enough to fit in the charging handle slot of an AR upper.

Hell, look at the HK P9S, tiny little thing.

I fixed it for you.

Another example is look at the Maxim 9.  Fixed barrel 9mm but uses a delayed blowback mechanism in an extremely compact package.

Here's another one for you
It's from a straight-pull bolt action, but the concept could be adapted in place of rollers if you got creative.

Waffles?

Who makes P90's?
Where is that company located?
What else is that country known for?

They’re also known for chocolate and an unholy mixture of French and German.

Interesting..Haven't seen that one before.  Thanks!