I was told by a CZ rep that the gas systems are all the same for the various barrel lengths for the Ms pistols but interested to hear if they tell you the same thing.

With my 11” 5.56 I have just shot one 30 round mag starting out at about 80 yards and walked into 50 yards and banged every steel target I shot at, various sizes. Mine seem to be dead on but I haven’t put anything on paper.

Op rod and gas hole position are the same for all the various pistol variants, however the gas tube (primarily the port sizes) differ between all variants. Additionally, the 8 and 9 inch guns use a different piston head design than the 11-14 inch barrels.

Have you verified this first hand by comparing the different versions personally? The port sizes was one of the specific questions I asked and was told they are exactly the same for each version, which surprised me to be honest.

Yes, thoroughly investigated

Very good, it sounds like and is verified that to swap a barrel between 11" and 14", you will also need a correct gas tube to match? Between an 8"/9" and a 11"/14", barrel, gas tube, and piston head are required?

I will be calling CZ today and will verify this while I ask them about my rear sight windage adjustment tolerance and also the trigger pin wobble I have. I spent some time with the pistol yesterday and can say the trigger pin wobble is not symmetrical, as in the right side is a larger hole with a good amount of play. Left side is smaller (caliper verified) and is tight. It's a Davidson's gun, so after my call with CZ may just try again with a tighter gun. Maybe the FNs I have spoiled me for extreme QC?

The gas ports are different sizes for the different barrel lengths. If you swap barrels you will need to swapt the gas system as well. As far as not being able to zero your sights, I would try a different set of sights to see if you can zero them. Might be an out of spec set of sights and not a canted rail.

Agreed, either out of spec sights or potentially barrel/receiver interface is out of square. Thanks for the input

Good to know, I was extremely skeptical of that. Hopefully that rep was also wrong about stocks not being here by the end of the month as well.

Let me know what you hear. My 14” barrel has ~200 rounds through it.

Might be a little while before I'm swapping barrels. CZ call resulted in them requesting I send Bren in to correct the rear BUIS offset issue. I'm impressed with their customer service so far. I measured barrel lateral offset from centerline with a quality straight edge, placed on the side of the upper receiver. Measured gap between straight edge to barrel shoulder just behind muzzle device. Less gap by 0.02" on right side, so there is some cant between sights and barrel Anyway, barrel swap will also require gas system components for that barrel length. Sounds like a good design from CZ and easy enough to garuntee function between barrel lengths

Today was a good day! My rear BUIS offset issue is solved. Waiting for the shipping label from CZ, realizing it would be Mon before I could send it in, I decided what the hell and took the Bren apart. Note: I've spent a good amount of time in several gunsmiths shops, so felt confident having a look myself. Barrel trunnion had the slightest machine marks and a rounded bur on left side, front bolt hole. Smoothed em out and reassembled. Didn't know torque order for barrel screws so mimicked SCAR pattern. 25 yard sight in has the aperture just 4 clicks from from dead center! Interestingly, groups moved down 1/2" from original sight in without me adjusting elevation. BUT and a big but, groups also tightened by almost half! Shot 4 & 6" plates at 100, and 10" at 200 just fine. These things appear to be a little rough on some internal parts and will require thorough break-in.

In 40 more rounds I'll be at 300 and will conduct an accuracy test with a bunch of different ammo. Will post a link later for that separate write up

Torque specs for the barrel screws is 70-inch pounds. 35-inch pounds for the front/rear sight per CZ. I asked them because HBI in their instructions for their handguard is 90-inch pounds. I set mine at the factory CZ specifications and have had no issues with any of my Bren 2's.

Thanks for confirming torque specs!

I wasn't sure on the order of what gets tightened first, second, etc... So Just tried to alternate.

Extremely happy with how mine is shooting now!

That carbine looks fantastic, but my concern is the release is 2020, and we know how CZ "releases" items (in very limited quantities over an extended period of time).  Normally, that's just fine, but our fucking firearms market in the US is so politically driven that the timing on this is extremely poor, at least for us as consumers.

The 2020 election is going to cause another panic.  You can damn near venture to guess the 2020 release of the carbine won't be until late into 2020, so the chances of scoring one for a decent price are slim-to-none.  To be honest, I've had an 11" Bren 2 in 556 on order for over 3 months.  I'll be lucky to see that rig before October of this year, so there's just no way they're going to be flooding the market with Bren 2 carbines when they can't keep up with the demand for the pistols.

ETA - Also, it appears being able to readily obtain ACR stocks is going to be a problem as Bushmaster is MIA (some news reports and posts speculating about what happened, but I sent them an email about a month ago and crickets).  In fact, try to find an ACR stock on the Bing right now...if you look at Brownell's, you'll see "discontinued."  Remington/Freedom Group is packed with such dizzy, out-of-touch, assholes that they cold have ceased production of 90% of Bushmaster's rifles and just stayed making ACR stocks (and adapters for the more popular firearms using them: SCAR's, Scorpions, Brens, etc...) and they probably would've been doing pretty damn good.

Just place em on ignore already. I sure as hell did. This is the very reason I frequent AR15.COM less and less these days. I jumped back on this week and have already placed four people on ignore. As I advance in years I have less and less patience for fools.

Back to the topic at hand, a friend has a line on 7.62x39 at a very decent price. Curious on latest time lines for 5.56/300 barrels and bolt kits.

From Dan Haga's instagram:

Post

Thanks for the update!

Like some other posts have indicated, ACR stocks almost impossible to come by now. Kinetic Development Group has taken over distribution of this item. They are marketing the ACR stock with SAR adaptor and it can be found easily on sites like OpticsPlanet, although at a big price increase.
Kinetic Development is offering them on their website. Black is out of stock right now, but supposedly more are on the way. If you need a coyote brown ACR stock, you're in luck, they have them in stock now. I ordered a black one before they ran out. Looking back, I should have ordered another one as the ACR stock just looks good on just about everything.

https://kineticdg.com/product/acr-folding-stock-assembly-coyote-brown/
https://kineticdg.com/product/magpul-acr-folding-stock-assembly-black/

I dont think we have any news in that regard unfortunately.

Considering they're selling out of 5.56 guns almost as soon as they enter the country and go onto dealer shelves I would imagine it will be a while.  Once again, I pray that my speculative notion is proven wrong.

I watched Military arms youtube channel today and he has been shooting a BCM carbine with no lube or cleaning 7000 rounds now without a malfunction. Has anyone been doing any endurance testing of the Bren 2?

I was just wondering the same thing...hard to find anything on this subject.

Not that I have any useful information to add, but I really cant understand never cleaning or oiling a gun EVER. I mean in the worst of cases combined with the maximum amount of laziness I could see maybe only wiping it down with a dry rag every 3k or so. But to specifically attempt to test a firearm with 0 cleaning over its life is like refusing to get an oil change in your car. Ya some guns+ammo+environment combos may be able to go longer than others, but none will go as long as they could have with just the bare minimum level amount of maintenance involved. Or in other words, why deliberately turn your 100k lifespan gun into a 50k life span gun?

At first, I was going to say that testing like this shows the absolute worst case scenario for the weapon.  Zombie apocalypse type of stuff where you just don't have time to clean your gun.

After thinking about it for another minute, I just can't imagine packing 50,000 rounds of ammo to shoot and not having the room for at least a small cleaning kit as well.

So, if not for simple extreme reliability testing, then the answer has to be... just for shits and giggles.

Hell even in the zombie apocalypse I'm pretty damn sure no one is humping 3k. (Not too mention you will likely melt your gas tube and destroy your barrel on an ar shooting that much in a short interval without some means of rapid cooling) and wiping down the inside of the gun with your t shirt is better than leaving it completely carbine fouled

My fat old rear end would be zombie food long before I destroyed a BREN 2 by not cleaning it...cardio was not my rule number one, tacos was...

In the early pages of this thread theres a link to an article where, iirc, both calibers are torture tested through thousands of rounds each. It's been a while, I dont remember the specifics

http://www.sadefensejournal.com/wp/torture-tests-the-cz-807-ai/

I think the Bren 2 would go forever if you allowed the barrel to cool down.  I think thin barrel and composite lower and internals would be a possible durability issue compared to an Mk18 but the Bren 2 has lots of pros over the Mk18 such as side charging handle, folding stock, much cleaner, not over gassed, can swap out barrels and calibers much easier/faster...I have a few thousand rounds through my Bren 2 and probably 6k rounds through my Mk18 and not any malfunctions. I do clean and lube them though. I think if I was to go to battle with 1 though Id still grab the MK18 first because Im still worried about how the composite lower and parts will hold up. If Bren 2 had an aluminum lower or even just composite lower all metal lower internals like the scar while keeping the weight same it would be a no brainer for me and the Bren 2 would be my choice. I broke the composite kdg acr stock when training with my scar 16 so thats why im a little worried about that. Time will tell.

This is a neat test on the 807. Looks like the rifle held up well with one extractor failure @ 6000 rounds. Note to self, buy extractor.

I hope that parts on the bren will last longer than 6000 rounds and that was just a fluke that the extractor broke.

I can't help but wonder if the II's charging handle might be the real weak link, there.  It's shuttle is plastic, and it sits in a very hot area.  Also, the II has a different gas system anatomy than the 805/807 tested; it's simpler, so I imagine it'd do better.

As far as heat dissipation, I'll be sending my barrels/piston components, firing pins/extractors out for Cryo. I've had parts done in the past, and I'm a believer in it. It defiantly works for heat-mitigation.

For all of you in Bren 2 land, I do have a current update from CZ in regards to stocks and 922R parts. I was informed this morning that stocks and the parts will be released ANY DAY, so check out their
website daily. I'm sure they'll sell out quickly!

I was thinking the same thing and am looking at options to start producing my own US made parts for these and others that need it. I have the operators who can run the equipment but need more info on the metallurgy design requirements for such components.

Machining it will suck; IIRC it has square holes & stuff.  Anodized aluminum for the shuttle would work; just be sure to make a knob that's covered in phenolic plastic so it can be used when hot.

I had a few ideas for improvements, namely how the shuttle latches to the trunnion for non-recip, but that's all at my last job so I won't develop it now.  But I didn't care for the handle design; it's totally hollowed out for the latches & seemed needlessly weak & complex.  It's like Germans got their hands on a SCAR.

Without putting in too much speculation to this, I'm looking at the charging handle, upper receiver and magazines as potential weaknesses. Receiver and magazines may interrelate here. The two mags that came with my 7.62x39 are excellent and have perfect fit in the lower. Three translucent/smoke mags do not have the same build quality, and are noticeably cheaper. They fit in the lower slightly higher when inserted to lock in. Loaded mags of the translucent type put upward pressure on the bolt carrier. Atleast mine do. Loading a fully loaded mag of each type into the weapon on closed bolt tells the story if you don't have calipers. Black mags take a tap, translucent take a slam, and one of mine won't actually lock in when fully loaded. Trimming them this evening ever so slightly to avoid mag push on the bolt carrier. The mag bodies are also softer and lack reinforcements like the factory mags in box.

I purchased my 11" 7.62x39 version to run it very hard. Will also be doing accuracy testing throughout the trial. I won't be doing foolish torture testing like mud baths and gravel in the bolt, just classes, training, and many many rounds of different ammo types in every weather condition. Will be writing up a blog post and linking here as I get data. My Bren 2 had an offset rear sight I had to fix first, but is now ready to go hard. Completed 300 round break in a couple days ago and have 900 rounds ready for tomorrow's snow storm. Accuracy testing first thing though, including cleaning and fouling shots between ammo type tests. Then will go 2k rounds without cleaning or a failure whichever comes first. After that will use the weapon as I would if my life depends on it. Cleaning/lubing as appropriate. 5k rounds already set aside, 5k more will be run after another accuracy test when first 5k rounds is reached. I've gone through several AKs with thousands of rounds, including a Norinco with 15k, so familiar with long runs on a weapon, but also keeping track and monitoring progress with good notes. Can tell you the magazines that are sold separately already worry me. Hopefully can find 10 or so of the original like the weapons ship with. Any leads on these mags?
Edit: will also be comparing to my SCAR 16 and 17 which also have had good runs in a bunch of conditions.

Couple of things guys.

I have a 9 inch Bren 2 MS.

I'm at 700 rounds through it.

The gun is set up as follows from tip to butt.

Dead Air Muzzle Brake
Scalar works 1.93 mount
Holosun 403R
Magpul ACR Stock
Dan Haga brace adapter
Tail Hook brace.

My intent behind the gun was to finally break into 7.62X39 and hunt hog with it.  Below are my observations.

The gun is quickly becoming my favorite centerfire rifle for a myriad of reasons.  Ive lusted over the gun for a long time and have waited patiently for them to enter into the states.  Is the gun perfect?  No, absolutely not but its pretty darned close for a lot of reasons.  I am running it with two of the older production smoked magazines and my observations mimic other posters here.  These magazines do not feel as sturdy.  They actually feel thicker as though the plastic walls are thicker in order to make up for the inherent weakness of clear polymer.  They're also definitively more ribbed along the spine which makes them a little bit less ergonomic than the standard black magazines.  Seating them on a closed bolt doesn't appear to be all that difficult at this time.

I have approximately 700 rounds through the gun with no cleaning, just lube.  Not cleaning a gun does not shorten its lifespan.  Abusing it does.  I wont be cleaning the gun but I will be adding lubricant periodically as ive always run my weapons wet.  To date, there has only been one malfunction but I believe that it was shooter induced.  The shooter was using a magwell grip and I think their finger got in the way causing a shell casing to fail to clear the ejection port resulting in a stove pipe.  Im chalking this up to the shooter and not the gun.

The front end of the gun is absolutely filthy.  I believe that there may be a bleed off port on the gas block which is resulting in the handguard collecting unburnt powder and all manner of filth. The front of the gun is literally turning brown with soot.

My gun ejects to 1 o'clock.  I feel like it may be over gassed just a tad but man does it feel good.  The recoil impulse is sharp but not "biting" and the sights return to their original point oh so well.  I absolutely adore the way this thing shoots with that dead air brake on it.  I cannot wait to suppress this thing but im going to have to figure out a port setting as im hesitant to drill through a nitride piece of steel resulting in a non nitride blast surface.  Im hoping that CZ will release gas blocks with suppressor ports already milled in.  The price of this should be relatively affordable since its a fairly small part, at least one would hope.

The controls are all really well laid out and I have zero concerns over durability of anything.  Despite there being a fair amount of polymer on the gun I have no issues with it and I don't forsee any failures.

I will be putting a huge amount of rounds through the gun as I intend to see how far and how long it will go.  Hopefully CZ will bring in spare parts as I intend to shoot this thing until it breaks and then report back.  By the end of the year I should easily have 20k rounds through it if all goes according to plan.  The only thing that may derail this test is my desire to pick up a 5.56 gun which will cut my round count down as I cant shoot both of them at the same time. :)

I adore this thing.

I also had a stove pipe early on and believe it was from the thing just needing some time to break in and/or magazine. They are a little rough at first. I'm not worried about any similar future issues though, as it has been doing well. Are you only using the windowed mags or some of the translucent type too? There is a definite difference in build durability between the two. The cheaper translucent mags don't give me much hope of high round count, but hope and reality may be different after a bunch of rounds.

Over gassed is a good possibility. What ammo are you using? I've noticed my 11" doesn't change ejection pattern between gas settings. Perhaps the "2" setting is not as small as needed? My Nomad will be run on it at 2k rounds, so a week or two from now. Will report as well.

Resist the urge for 5.56 and get your 20k rounds out of it! Mine will be getting 10k by mid summer, and hopefully much more within a year. Would be much more meaningful to have a few of these being reported on.

I know for a fact the S receiver had some weaknesses (split like lumber along the now-absent lightening cut down the side after a kaboom) that have since been addressed.

Biggest weakness of the MS remains a really kludgy and inefficient way of attaching handguards.  Also making the gas block just barely too tall to fit inside the receiver profile, for no discernible reason.

You had an S model upper receiver split on you? My S models have been perfect. I have thousands of rounds through mine.  Only thing I prefer on the Ms model is the HBI extended handguards. If there was a way to extend the handguard a couple inches on the S model it would be near perfect in my opinion.

Odd question buy I was wondering if anyone can tell me if magwell on the Bren 2 can be removed with an empty mag inserted?

ETA: interested in 7.62 and 5.56

Do you mean the complete lower assembly or just the magwell insert?

Honestly not sure. Saw a video that you can install a retro magwell but possibly might have been a different model? Looks similar to the STANAG magwell for a G36.

Ya that was the previous model the 805 bren.

Im using the translucent mags.  I have a few of the windowed ones that are sitting in the safe as I'm curious as to how durable the translucent, older production mags really are.  They feel a little on the flimsy side but ive been surprised before.  Only time will tell how long they last before they give up the ghost.  I will obviously report back if they fail and at an approximate round count.

Just looking at the gas block itself, the hole sizes are readily apparent.  The "adverse" setting looks positively huge.  I did notice a little more violence in the action when I set it to the larger of the two gas port holes.

For the foreseeable future, I will be running only wolf bi metal steel cased ammo through the gun.  I may group it down the road with some select hunting ammo once I narrow down what I would like to use.

Eventually, when the Resonator K clears, ill probably exclusively run this gun with that can on the end.  Here's to hoping its not another thirteen month wait for that suppressor lol. :)

Also, one more thing I left out of my review.

The trigger, while fantastic isn't perfect for me.  Its VERY easy to shoot well but its also VERY easy to short stroke because of the huge amount of over travel present in the system.  HBI solves this with their trigger shoe.

I recently picked up a 5.56 ms. Really great gun, very happy with it. I have around 500rnds through it with no issues. On a couple of occasions thought I’ve found metal shavings in the lower when cleaning. Can’t see where they would have come from. Has anyone else noticed this?

Please explain how you know that the S Receivers have weaknesses in the lightening cut and that they split like would there? Lots of us here have the S models and have heard nor read anything about this anywhere until now.

Really...? Funny how none of us that own that version have ever heard of any issues. Even more funny is the fact that the military version uses the same cut and they haven't had any issues...at least none that my family back home in Slovakia and the Czech republic ever heard of and they use them for active duty. Please enlighten us and point us in the direction of this information we seem to be missing.

Meh, he specifically mentioned this happened during a catastrophic malfunction. When you blow a gun up, something is going to fail, and if you blow it up extra good, multiple things are going to fail. It's not outlandish in the least that, in a situation in which pressure far exceeds the system's limits, that the receiver would be far more likely to fail at its thinnest sections rather than its thickest.

Heck I've seen ar15 uppers literally sheared in half,  ak's blow a chuck right off the right side of the receiver, and barrett 50 receiver open up like a damn bananas and many many other catastrophic malfunctions. I even once turned a remington 700 into a modern art piece by accidentally combining a squibbed barrel with a double charge, the forend could be aptly be described as "evaporated"

So the real key here is, dont shoot shit ammo, make damn sure your bore in unobstructed, and always wear your eye pro

I hear ya and agree that a kaboom in any firearm can cause severe damage. Seen many examples. Having said that, it does not mean that the 2s or true military series has a design flaw or defect as he was trying to imply simply because they changed the cuts on the 2ms. I had heard that it was more a cost cutting measure. Less cuts means less expensive to make so can be brought to market at lower price point in the US while including the redesigned forend.