Update as of 22August below in Post #7
2nd Update 27Aug2023 - 100% success shooting everything tested below in post #21

Short version: ran flawlessly through 300 rounds of various brands of 115 grain 9mm ammo using the included K lifter. 4 failures to eject out of 50 rounds of 124 grain NATO using the K lifter-- most likely needs an M lifter. Recoil impulse is pretty close to an MP-5; way better than any blowback 9mm like the CZ Scorpion or Ruger PC Carbine, and noticeably softer than the CMMG radial delay with a standard carbine buffer/spring.

Long version: Within two hours of receiving my upper 10 days ago, I got an email from MEAN asking me to send my bolt carrier group back to them via the prepaid box they were sending me. I didn’t even test fire it, I just field stripped the upper and degreased everything to see how the system worked. (It was really packed with a blue grease of some sort.) I sent it back and they returned it to me within the week.

In addition to the complete upper, it also came with a manual, a couple of stickers, warranty card, additional H lifter for lighter loads and two EndoMags. Buyer beware, the EndoMags are NOT complete magazines-- you still need to provide your own Magpul M2 or M3 30-round magazines to install the EndoMag conversion kits into!

The manual is quite thorough and refreshingly brief on safety warnings and heavy on technical information. While it may appear intimidating to some people, if you handle the parts, the system is actually quite simple and it is quite easy to conduct “Normal cleaning, Major Cleaning, and Depot Stripping Level 1.” I have not attempted “Depot Stripping Level 2” thus far, which allows you to replace the ball bearings, extractor and ejector, but from the detailed pictures in the manual and handling the parts, I believe it will be straight forward like many other firearms. In the back of the manual are 2 graphs that illustrate which lifter you should use depending on the ammo you are using and if you are shooting suppressed and or full auto. Use one graph for barrels shorter than 11.75”, and the other graph for longer than 11.75”.

The upper comes with MEAN Arms muzzle brake, which I consider kind of worthless for a 9mm carbine. In previous carbines I have shot, I suspect the mass of the brake probably did more to tame the rise of a 9mm carbine barrel than the actual gas porting. But, the brake looks nice and is easy to time due to the reverse thread jam nut. (As it turned out, it wasn’t obnoxious when shooting with it installed. Now that I have successfully test-fired the upper as designed by MEAN Arms, I will be removing the brake as I intend to shoot it mostly suppressed.)

The barrel is a “medium” profile barrel-- it does get hot after shooting rapidly for a bit, but it doesn’t take a long time to cool down between strings, and it handles easily and balances well with a light Magpul stock on the butt end. I have not removed my handguard, but the barrel nut may be removed/installed by using a standard 1-1/4” wrench according to the manual.

The polymer handguard is much nicer than I expected. I actually like it and will keep it, which surprises me. It is fairly slim in profile despite being polymer and it visually blends well into the profile of the upper receiver. While shooting, the barrel temperature reached at least 170 °F while the hottest the handguard reached was 114 °F which was still very comfortable to hold. The front of the handguard is approximately 3/8” behind the rear of the muzzle brake jam nut so there is room to turn the jam nut off and remove the muzzle brake without removing the handguard. I have not attempted to install any MLOK accessories to the rail thus far, so I cannot speak to that feature. As Amphibian mentioned in a previous post, the handguard has two opposing small screws pinching the top of the handguard to the barrel nut, and they do have some sort of thread locker on them.

The receiver is slick sided-- no forward assist, as there are no forward assist grooves on the bolt to cam against. There are also no feedramps cut into the upper receiver, the only feedramp is one large one at the bottom of the barrel extension. I suspect there is no need, as the 9mm bullet is so much larger in diameter and the EndoMag follower guides the round higher/earlier into the boreline without ever coming close to the receiver itself. There are two guide rods that appear to be stainless steel that run from the barrel extension to the back of the upper receiver that the bolt carrier rides upon. The rods (rails) are fixed in front by the proprietary barrel extension that the bolt locks up into, and in the rear are held in place by a polymer piece that fits in the fire control slot just forward of the rear take down pin lug. I see absolutely no reason why a standard AR upper could not be used with the MEAN Arms barrel extension, guide rails, rear polymer rail locator, and bolt carrier if the upper was damaged or if MEAN decides to sell the system as a separate kit in the future. The ejection port cover is enclosed on the rear of the hinge lug and requires removing the handguard to swap the door if it were to be damaged or you wish to install a custom door of some sort.

The charging handle appears to be a standard ambidextrous charging handle that can be used on a typical 5.56 NATO AR-- it has a hole in the front for a gas tube although the bearing delay system does not use a gas tube. The latches seem to be a cross between a Giessele and a Raptor in feel-- not as curved as the Geissele, not straight like the Raptor and it does not have any checkering on the front face, but it isn’t needed as the curve keeps your finger in place. There is a bit of a raised lip to reduce gas blowback between the receiver and charging handle, and it operates smoothly without pinching. So far I like it and will keep it in place.

Finally, the heart of the system-- the bolt carrier group. It really breaks down into 6 parts/subassemblies -- the bolt carrier, firing pin, firing pin spring, lifter, bolt extension and bolt. All the main components have some sort of coating on them-- I do not know what it is, but it appears similar to NP3 and like NP3, makes it extremely easy to clean carbon and other residue off the parts after shooting. I have not detail stripped the bolt beyond this stage thus far, but it was possible to clean it thoroughly using Q-tips, patches, a nylon brush and solvent. It isn’t easy cleaning around the ejector in the middle of the bolt face, but it is possible. In the future I will probably just drop the bolt subassembly in an ultrasonic cleaner, although a friend suggested that he might drop it in a small bottle of solvent and let it soak for a while, which should work, too.

While on the subject of cleaning, I discovered the barrel extension was actually pretty easy to clean after pulling out the shooter swabs. https://www.midwayusa.com/product/1903350379 I used solvent dipped swabs and Q-tips to thoroughly clean the barrel extension and then cleaned the barrel as usual.

I wanted to test fire the upper as it came from the factory to make sure everything worked before I started modifying it, so I left the muzzle brake in place for the first trip to the range. I brought an assortment of 115 grain ammo as well as some SAR 124 grain NATO 9mm as my PTR needed approximately 500 rounds of hotter ammo run through it in initial break-in before it ran successfully. Starting with the 124 grain NATO ammo, I had a failure to eject within the first 5 rounds. The round extracted but was left hanging in the ejection port as a “smokestack” with the partially closed bolt trapping it. Interestingly, the second round was partially chambered-- the bolt just couldn’t close behind it because the previous brass case was keeping it open. We also noticed that the ejection pattern was wild when shooting the 124 grain ammo. I cleared the firearm and continued with a second similar failure several rounds later. I then switched to some Federal 115 grain ammo and it ran flawlessly through 50 rounds. I then switched to 115 grain CCI Blazer brass and it ran flawlessly as well. I then switched to 115 grain Magtech and it shot that flawlessly, too. The ejection pattern was incredibly consistent with the 115 grain ammo-- we could have captured the brass in a 5 gallon bucket placed around the 4:30 position about 6 feet from the shooter. I then switched back to the 124 grain NATO ammo and it had 2 more failure to eject to finish out the box of 50. I then decided to try 115 grain Federal American Eagle Aluminum Cased ammo (NOTE: the MEAN Arms manual specifically states NOT to use aluminum cased ammunition on page 42.) I was pleasantly surprised that it ran flawlessly as well. I ended up shooting 300 rounds of Federal, CCI and Magtech 115 grain 9mm without a single failure (including the aluminum cased stuff), and 50 rounds of SAR 124 grain NATO 9mm with a total of 4 failures to eject. I suspect the 124 grain NATO ammo would work just fine if I used a lifter designed for more powerful ammo-- perhaps an L or M lifter.

I mounted a red dot micro for an optic and was happy to find it relatively easy to keep the dot on target while shooting double and triple taps. I was surprised that the 124 grain ammo, while unreliable, was really accurate in this upper (cloverleaf clusters at 25 yards with a red dot is pretty darn good in my book). I am really looking forward to seeing what it will do with 147 grain ammo. The 115 grain brass ammo shot only slightly larger groups, but the aluminum cased ammo was more like 4 or 5 inches for 10 shot groups. Maybe it is just the ammo but my Glocks shoot the aluminum CCI and Federal pretty well, so that was a bit of a surprise.

I don’t think I will ever use the H lifter that was included with my 11” barreled upper. It probably is much more useful for those that shoot the 4.5” or 7” barreled uppers. My next steps will be removing the muzzle brake and shooting 147 grain subsonic ammo both suppressed and unsuppressed. I suspect I might need to order an L or M lifter (or even greater) for success while shooting suppressed 147 grain loads, but we will see. I am also curious to see what this barrel will chronograph at-- it will help me determine what lifter I will need.

Possible concerns: the MEAN Arms manual mentions an optional bolt fixture for assisting in removing and installing the extractor and ejector. It remains to be seen how difficult this task is without the fixture. The preventative maintenance cycle for suppressed and full auto use calls for replacing the ejector spring, ejector retaining pin and extractor spring after 2500 rounds and additionally replacing the firing pin spring, the 3 ball bearings and the bearing retainer ring every 5000 rounds. I do not know how expensive these parts will be-- they are relatively minor parts so hopefully they will be easy and inexpensive to purchase as the duty cycle is rather short compared to other firearms.

So far I really like the MEAN Arms bearing delay upper-- it has the potential to be as soft shooting as an MP-5 but have much better ergonomics and is much easier to add accessories such as a red dot.

Fantastic write up! I am awaiting the 4.5" version to be shipped. Hopefully this week. I mentioned to Tom it will be run full auto / suppressed and he did not mention different parts for each application. I'll figure that out going through the manual.

I ran about 300 rounds of factory PMC 124 Gr and some factory 158 Gr IMI and my 147 Gr reloads.    
I tried the H, K and M lifters.  I am getting failures to eject as well with all the ammo.  I did run 50 rounds of 124 Gr Geco and that was problem free but 50 rounds isn't (2) 30 round mags.  I haven't been able to run (2) 30 round mags flawlessly.
I didn't have any 115 Gr to test as I really want to run 147Gr subsonic 99% of the time.

I think the extractor is too aggressive...especially considering this design uses a fluted chamber to also aid in extraction.  I tried to take the extractor apart according the manual but feel like if I use more force I may break it.  I emailed them asking for next steps.

Excellent write up! Thanks for the great information!

Is the extractor too aggressive, or is the ejector not aggressive enough?  Most ejectors pivot the cartridge around the extractor from the opposite side of the bolt, giving the ejector the most leverage possible.  From a physics perspective, once that center-bolt ejector starts pivoting the cartridge, the cartridge base will instantly be at an angle and all of the leverage to eject comes from the side nearest the extractor, giving the least amount of leverage. Most of the weight of the cartridge base will now be on the wrong side of the ejector's contact point. I'd expect the cartridge case to twirl around and get caught in the action instead of being flung out the port.  Maybe I'm wrong, but it seems like a bad ejector design.

Maybe it is a bit of both.  The ejector had about 8 lbs of force new and it is down to about 6 lbs.  The extractor was a little under 4lbs new and still the same.  When clearing the jam, I have to pry the spent case off the extractor.  I think if you just broke the corners off the extractor or maybe at least de-horn it, it may be fine.  I don't feel the excessive headspace slop with this design like I do with the CMMG RDB so I'm hoping it isn't prone to fast ejector spring failures like the CMMG RDB.

The face of the ejector could be angled to address some of that.

But I’m not sure we need to go that far yet, this could be as simple as a variation of rim thickness on the ammo or a tiny burr on the extractor.

Update 22Aug2023 – 100% success shooting 147 grain suppressed and unsuppressed in 11”

2nd trip to the range, ran flawlessly through:
50 rounds of Browning 147 gr FMJ unsuppressed
50 rounds of Browning 147 gr FMJ suppressed
50 rounds of my subsonic 147 gr reloads unsuppressed
50 rounds of my subsonic 147 gr reloads unsuppressed
100 rounds 115 gr FMJ unsuppressed

All using the standard K lifter with a standard carbine buffer and carbine buffer spring, which is also what I used shooting the 115 grain and 124 grain ammo on the first range trip. I was giddy that the subsonic 147’s shoot even softer than an MP5!

I removed the MEAN Arms muzzle brake and direct threaded an Octane 45. it was very gassy shooting suppressed, but that was not a surprise as the Octane is known to have a lot of back pressure and gas in general. I will be asking MEAN Arms tomorrow if a different lifter might reduce the excess gas without effecting the reliability. In the meantime, I will probably apply some RTV to the charging handle.

I chronographed the loads as I shot-- the Browning averaged 1084 fps out of my 11" barrel and you could hear the supersonic crack more often than not. My reloads were subsonic at 937 fps out of the 11" barrel (they run 1044 fps out of a 16" barrel.) I was focused on getting good chrony numbers and watching for reliability, so I did not shoot for accuracy this trip, but next time I will make note of the accuracy using 147’s.

Because Amphibian has had problems with 147 grain ammo, I started with a magazine of 5 rounds. When it ran perfectly, I loaded up a mag of 15, and then a full mag of 30 for both the Browning ammo and my reloads and both suppressed and unsuppressed conditions. I had very little time and that was all I could shoot last night, but all 600 rounds of SAAMI spec’ed ammo that I have shot and my own reloads have been 100% reliable through my 11” MEAN Arms upper. The only ammo I have had problems with thus far is the 124 grain NATO ammo that is hotter than SAAMI spec, and I suspect a different lifter will solve that problem.

For those planning on removing their muzzle brakes, there was room for a wrench on the jam nut and another on the brake without having to remove the handguard. I was surprised to find some form of thread locker on both the jam nut/muzzle brake and on the muzzle brake/barrel interfaces-- MEAN Arms doesn’t want that muzzle brake to come off unintentionally! It was not hard to remove-- just follow the illustration in the manual as to the direction as the jam nut is a reverse thread.

While typing this up, I just received a phone call from MEAN Arms. They have been working like mad trying to replicate Amphibian’s system and they believe they have solved his issues, and they think it will take care of my 124 grain NATO ejection issue, too. MEAN Arms has been absolutely phenomenal in providing customer support; us early adopters can be kind of demanding with special requirements, but MEAN Arms is taking us seriously and resolving the issues we are finding/creating. The average shooter is never going to need to contact MEAN Arms, but they really mean it when they say their products have a Lifetime Warranty and they want to help if you have a question or issue.

Amphibian, have you tried combining the Mean Arms and the RDB yet?  

When I started reading this thread, I somehow knew that would pop up

Attached File

@fullauto01

Thank you for the detailed write-ups. Apologies if I missed it, but what lower and mags are you using with this upper?

I already have an SBR'd DDLES Glock mag lower but would also like to have the option of running on an RR M16 with Colt mag block from time to time as well. I never got into the ENDO Mags environment and don't really want to at this point.

I didn't see any mention of Colt mags/lowers on the Mean website, but it does say it's GTG with MIL-SPEC lowers, so I'm guessing that means Colt mags wouldn't be an issue.

Please see what I posted in the MEAN Industry thread page 2 on 8/1/2023 7:21:35 PM EDT
Scroll almost all the way to the bottom of the page.
https://www.ar15.com/forums/Industry/Bearing-Delay-Upper-Receiver-Assembly-updates-information-and-resources/817-303326/?page=2

Uh...no...no plans for that

Yes, support has been great!  I am expecting a part to get delivered today.

@towerofpower94, good catch, I totally forgot to mention the mags and lower I was using. All my testing thus far has been on a semiauto stock AR lower that has been SBR'd with a stock carbine buffer and carbine buffer spring. As for mags, I am using multiple Endomag inserts in Magpul M3 mags. I did remove the muzzle brake to be able to thread on my Octane 45 can, but I plan on installing a tri-lug when the parts come in. Amphibian pointed you to the best info in regards to using Colt mags.

I had to let the carbine sit dirty for a day so I expected to need more elbow grease to clean it tonight, but I was surprised that it was easier to clean this time. It was filthy due to the back pressure of the suppressor, but it wiped off quite easy. Whatever coating MEAN Arms chose for the BCG was a great decision! As I mentioned in my first review, using Tipton shooting swabs makes cleaning the barrel extension where the bearings lock up a whole lot easier. The manual suggests using a 12 gauge shotgun brush but either way, I find the extension a whole lot easier to clean than getting behind the lugs of an AR or trying to using the MP5 specialized brushes and mops. When I first got the upper, it came from the factory with some form of blue grease packed in it. I cleaned it all off before applying Lubriplate SFL0 grease (tip of the hat to Grant Cunningham who turned me on to the stuff a long time ago) and then a little gun oil to the tight places where the grease might not reach. The manual calls for using gun oil, but the grease stays in place better and doesn't evaporate as quickly as oil, so I will stick to using both.

If I sent you a box of ammo, would you try it just for grins & giggles?  

A scholar and a gentleman. Thank you

Thank you for the follow-up. This might just be my way ahead as far as a non-blowback solution.

Umm....nah...maybe for a CASE....I would do it...lol

Sorry, don't have case funds loose at the moment, just wanted a 50 round report - it works against all common sense, or predictably didn't work.

Update 27Aug2023 – 100% success shooting EVERYTHING tested in 11”

Short version: after MEAN Arms BCG modification
100 rounds Federal 115 grain FMJ – 100% success
100 rounds SAR 124 grain NATO – 100% success
60 rounds unsuppressed Browning 147 grain FMJ – 100% success
90 rounds suppressed Browning 147 grain FMJ – 100% success
Todays SUBTOTAL: 350 rounds – 100% success

Longer version:
A week ago MEAN Arms contacted me and asked me to ship my BCG back to them (they sent me a prepaid label) as they thought the same slight tweak that could get it to run Amphibians subsonic reloads would also solve my issue shooting the hotter than SAAMI spec 124 grain NATO ammo. In fact, they figured I would probably be able to run everything I wanted to just using the K lifter that comes standard with the upper. While I originally shot the NATO ammo because I thought it might help with break-in, I really was not intending to shoot it through this upper in the future as I am more likely to shoot it with cheap 115 grain ammo or suppressed with subsonic 147 grain rounds. But, since I brought the issue up, I figured I might as well try it again when I got my BCG back.

MEAN Arms said they would most likely be able to turn my BCG around with the fix on the same day, and sure enough they did. Their shipping wizards must give their local postal carriers free ammo or something, because somehow they managed to get my bolt from their facility in Georgia to me in Michigan in less than 24 hours, just in time for me to test it again this weekend. Looking at the BCG, I could not see what they modified, but the bearings and extractor did appear to be cleaner than when I sent it to them (they might have been new replacements?)  I did clean everything before I sent the BCG out but these were shiny, not just clean.

When I shot it suppressed last time, I found the upper to be gassy, especially with my subsonic load, so while my BCG was out I decided to apply some RTV to the rear of the MEAN Arms charging handle. The process was straight forward and the ambidextrous charging handle levers did not cause any difficulties applying the RTV. I did use a little painters tape along the edges to prevent RTV from possibly leaking in the gap between the main body and the levers, but I don’t think that step was necessary as the tape was clean when I peeled it off the charging handle.

I again used the same lower as I have used previously with the same standard carbine buffer and carbine buffer spring. Having confidence in the 115 grain factory ammo, I started with 30 round magazines and shot 100 rounds of Federal (three 30 round magazines followed by a partial magazine of 10.) It shot as expected with no issues whatsoever. I then loaded up the SAR 124 grain NATO ammo and shot the same sequence. This time it worked perfectly, too! :) I then shot 60 rounds of Browning 147 grain factory ammo (two 30-round magazines) and it also shot perfectly, as expected so I decided to direct thread my Silencerco Octane 45 suppressor on the barrel and finished shooting another 90 rounds (three 30 round magazines) of Browning 147 grain ammo. I did not have time to load any of my own subsonic 147 grain ammo this week, but it ran 100% last week so I expect it to run flawlessly next time I go to the range.

For those keeping track, that is 350 rounds today and 1000 rounds total run through this upper thus far. With the latest changes, it appears my MEAN Arms upper is now 100% reliable with everything I am shooting through it. The RTV cut down the gas to the face considerably, it is much more pleasant to shoot. I continue to be impressed with the handguard as despite the suppressor increasing the barrel temperature to 197 °F while shooting, my hand remained comfortable holding onto the handguard even directly over the barrel nut (114 °F.) So far all my shooting has been on an indoor range, but I can see this handguard being a real winner when laying out in the direct summer sunshine. We will see how it does in the cold, but that testing is going to have to wait for a few months. ;)

I'm hoping they start selling their bolts and barrels soon.

I have an integrally suppressed upper that I would LOVE to try this on.  I had spoken with them when they were first announced and they said they were starting a customer list for just components and I was on it.  So, I'm hoping that I'll get a notification once they are caught up on their upper sales.

How was the controllability? Were you able to keep 3 rounds of full auto, center mass at 15-20 yards?

Thanks!
Bill

Anyone try JHP Subs like 147 grn with or without a Suppressor.   I have Ball, just more JHP.

@splicer I ran a couple of magazines of 3 different hollow points ranging from 115 to 147 grain (all brass cased) with no issues for any of them. I was using the MEAN Arms Endomag/Magpul combo as usual.

I put the MEAN Arms 11" upper on a different SBR lower with a VLTOR A5H2 buffer system (stock VLTOR spring) and it functioned perfectly, but it really changed the recoil impulse. It had a rolling effect from the heavier buffer that I felt was harder to keep the red dot on target. A friend that shot it said it was making him seasick shooting it. I will keep the MEAN Arms upper on a standard carbine buffer equipped lower-- it really runs well with that set up.

I have one of their polymer handguards on a regular DI build and like it a lot, although I haven't fired it yet. Installed easily and looks great