Bren 2 9" FTE/Stovepipe issues

[Archos]

Other users had asked for more info on my pistol so I figured I would post here as well. My bren 2 was having multiple failures to eject and stovepiping fairly often. On average I would get 1 stovepipe per magazine. Many times the empty case was flipped 180 degrees and wedged between the chamber and bolt while attempting to chamber a 2nd round. The pistol would have these malfunctions with all the ammo I was using, Wolf FMJ, HP and Golden Tiger FMJ. I also tried both gas settings with no change in performance The original video I took is here:
https://youtu.be/L-cUi9Aw11g

For the rest I'll just copy my update from Arfcom.


Well, after 5 weeks I received my 9" Bren 2 back from CZ. I was having stovepipe malfunctions at a frequency of roughly 1 per magazine.

When I received the email stating what had been done to correct the problem I was not very optimistic that the issue would be fixed, however I figured I would give it a shot.


Warranty sheet: https://photos.app.goo.gl/8gc4QTjyLs8yNBkj7

I received the pistol yesterday morning and was lucky enough to slip away to the range to quickly run 100rnds through it for a test fire.

The pistol made it through the first magazine of 20rnds without a hitch. I then loaded a different magazine with 30rnds which the pistol also made it through. The next magazine was loaded to 30rnds and unfortunately at the tail end of the mag I had a stovepipe, I would guess right around 75 rounds into the session.

Stovepipe: https://photos.app.goo.gl/Lu7QmuThA8DqSD1N8

After clearing the malfunction I burned off the remaining ammo I had without a hitch. All in all I shot 100 rounds with one stovepipe. I'm also going to add a picture of the wear on the front of my ejection port for all to see, I'd like to know if any of you have the same wear?

Ejection port: https://photos.app.goo.gl/MrM82f29YvoKeRAw5

Also here is a picture of a spent case, this case barely made it out of the chamber when fired. This is the worst example I could find.

Bent case mouth: https://photos.app.goo.gl/YpqzTaboNPcqQh8YA

This bren has roughly 400 rounds through it at this time, I'm going to contact CZ about the pistol and see if they can take another look at it.

[MeatAxe]

So it stove piped on both gas settings and CZ’s remedy was to clean the gas port...I wonder if the gas port hole is too small / under gassed?

Also, how did it shoot before you put the HBI hand guard on it?

[Archos]

From the ejection pattern of most of the rounds and the recoil impulse I find it hard to believe that the pistol is undergassed, but I could be wrong.

Before replacing the handguard I only ran roughly 100 rounds through the pistol. I didnt have any stovepipes within that time frame. The only issue I had was with my buddy attempting to chamber a round from a full magazine.

I have adjusted the torque on the handguard screws between range sessions to check if improper installation was an issue, however there has been no change in performance.

[Aries144]

Try something: disassemble the weapon, remove the bolt, cam pin, and firing pin from the carrier, reinstall the carrier and recoil assembly, and see if the carrier binds at all when it's near the chamber. It shouldn't bind or experience any resistance at all.

[MeatAxe]

Other users had asked for more info on my pistol so I figured I would post here as well. My bren 2 was having multiple failures to eject and stovepiping fairly often. On average I would get 1 stovepipe per magazine. Many times the empty case was flipped 180 degrees and wedged between the chamber and bolt while attempting to chamber a 2nd round. The pistol would have these malfunctions with all the ammo I was using, Wolf FMJ, HP and Golden Tiger FMJ. I also tried both gas settings with no change in performance.

Looking at your video, it appears that the first rounds are barely getting ejected before it stovepipes, subsequent rounds appear to eject normally, then suddenly stove pipes. Is it certain magazines or ammo that is worse for this?

I'm wondering if maybe the gas port / gas block are misaligned / misshapen or maybe drilled too small? Seems like gas gets clogged up and it stove pipes, gets burned clean with subsequent rounds and then starts the clogging / stovepipe cycle again. Can you get a bore scope and look at the gas port from inside the barrel?

Other than that, before you send it back to CZ, you might reassemble the gun in the original configuration with the OEM hand guard and see if it works better or not. I'd use new screws (torqued to 65 in.lbs. as per CZ) and nord lock washers (available from Fastenal) as the originals get stretched and jinked up from disassembly / assembly and locktite residue. I'm just not a fan of this aftermarket hand guard configuration - where you go from 3 rails and 15 screws to 2 rails and 4  screws...

Good luck!

[tskunk]

My 14" 7.62x39 started having the same issue after I installed the HBI handguard (700 rounds shot before the hg arrived with 0 failures). I hit up HBI and they recommended lowering the torque spec to 50-70 inch lbs. Doing that has so far solved my issue (~300 rounds without a failure).

[MeatAxe]

My 14" 7.62x39 started having the same issue after I installed the HBI handguard (700 rounds shot before the hg arrived with 0 failures). I hit up HBI and they recommended lowering the torque spec to 50-70 inch lbs. Doing that has so far solved my issue (~300 rounds without a failure).

Initially HBI recommended 90 in.lbs. Some had cycling issues so they reduced it to 70. CZ recommends 65 in. Lbs.

Apparently, the Bren 2Ms can exhibit some sensitivity to changing the hand guard configuration from the OEM set up (3 rails, 15 screws) to the HBI / CZ 922r compliance hand guard (2 rails, 4 screws). Although I did not have any cycling issues with the HBI hand guard, I did notice that ejected cases had heavy streaks of carbon running down the length of the cases (both brass and steel), which was not seen with the OEM hand guard set up. 

This past weekend I changed back to the OEM hand guard set up and fired @ 200 rounds: there were no carbon streaks on the ejected cases (brass or steel). There was some carbon build up around the case mouth to the shoulder on spent steel cases, but no carbon at all on the outside of the brass cases.

[CZ come CZ go]

Since the outer diameter of the barrel for both the 556 and 762 are the same, that means the 762 has thinner walls due to the larger round.

It seems like the thinner walled 7.62 barrel is susceptible to being squeezed out of spec when over torqued.

[Magsz]

Since the outer diameter of the barrel for both the 556 and 762 are the same, that means the 762 has thinner walls due to the larger round.

It seems like the thinner walled 7.62 barrel is susceptible to being squeezed out of spec when over torqued.

Please elaborate on this.  I'm not sure i'm following.  There is no way a steel chamber is deforming with 90 inch lbs being applied to it.  Please explain what you mean by the above post.

To the OP:  I'm in the same boat brother.  I'm going to wait and see what happens with my gun when it comes back but i'm getting ready to divest myself of the platform.  I don't have the patience for what may end up being a half baked americanized design.  If the original intent behind the MS platform, ie a modular front end cannot be realized this gun is all but useless to me from an ergonomic standpoint.

[Archos]

Adding to this post as I have also posted in the Arfcom thread as well.

After only 2.5 weeks into its second trip to CZ I received notice that my pistol's warranty work was complete. I was also able to speak with Mike, one of the gunsmiths over at CZ who worked on my firearm.

Mike told me that he had broken down and inspected my firearm for any issues that could explain my stovepipes. The only thing he was able to find was an excessive build up of lacquer in the chamber. He explained that due to the build up the cases were sticking to the chamber and thus creating stovepipes.

Mike went on to explain to me that the lacquer coated steel case ammo is the culprit, and that the lacquer melts and sticks to the chamber upon firing.  He did say that polymer coated steel case would be fine to shoot and would prevent these malfunctions.

 

Now, my understanding is that the lacquer doesnt melt off the case, but rather that the steel doesnt expand as well or as quickly as brass, thus allowing carbon and other crud to wedge itself between the case and chamber.

The other thing that bothers me is the fact that I have shot maybe 60 rounds of lacquer coated ammo through this firearm, not to mention that my last range trip the pistol malfunctioned prior to shooting the lacquer coated Golden Tiger.

Either way I told them I'll give it a shot, if I end up having another malfunction I'll be sending it back to CZ. Its extremely frustrating that this pistol has so many issues, when my 556R, made by SIG has no issues in the thousands of rounds I put through it.

[MeatAxe]

Adding to this post as I have also posted in the Arfcom thread as well.

After only 2.5 weeks into its second trip to CZ I received notice that my pistol's warranty work was complete. I was also able to speak with Mike, one of the gunsmiths over at CZ who worked on my firearm.

Mike told me that he had broken down and inspected my firearm for any issues that could explain my stovepipes. The only thing he was able to find was an excessive build up of lacquer in the chamber. He explained that due to the build up the cases were sticking to the chamber and thus creating stovepipes.

Mike went on to explain to me that the lacquer coated steel case ammo is the culprit, and that the lacquer melts and sticks to the chamber upon firing.  He did say that polymer coated steel case would be fine to shoot and would prevent these malfunctions.

 

Now, my understanding is that the lacquer doesnt melt off the case, but rather that the steel doesnt expand as well or as quickly as brass, thus allowing carbon and other crud to wedge itself between the case and chamber.

The other thing that bothers me is the fact that I have shot maybe 60 rounds of lacquer coated ammo through this firearm, not to mention that my last range trip the pistol malfunctioned prior to shooting the lacquer coated Golden Tiger.

Either way I told them I'll give it a shot, if I end up having another malfunction I'll be sending it back to CZ. Its extremely frustrating that this pistol has so many issues, when my 556R, made by SIG has no issues in the thousands of rounds I put through it.

The problem is Lacquer?

On a AR-18 based Czech gun built to shoot steel-cased, lacquer-coated 7.62x39 ammunition manufactured in the former Warsaw Pact?

Sounds like a load of BS to me, disinformation used to obscure the real problem (which CZ probably has no grip on at this point).

Here are the common denominators that I see on all these guns getting jammed up:

1. Bren 2Ms model. Check

2. 7.62x39 caliber. Check.

3. Aftermarket hand guard. Check.

4. Reduction from 15 torqued barrel / hand guard screws to just 4. Check.

Anything else?

I'm no gunsmith or engineer, but I never thought much about the idea of going from 15 torqued screws and an integrated fore end on the OEM 2Ms to hold the barrel, "hand guard" and receiver together, and then paring it down to just 4 screws (of ever changing torque specs) to hold the same or greater stress load with an extended hand guard. Color me skeptical.

ETA: I did see one 2S model on here having these troubles, but it was fitted with aftermarket pica tinny rails and missing some torqued screws.

[Archos]

I highly doubt the issue is with the aftermarket handguard. The carbine also uses this style of attachment for the handguard, and you don't see any issues with them. In fact, you don't see any issues with the 5.56mm pistols and aftermarket handguards at all. There are many other rifles out there that use the same style of barrel attachment, in .308 for that matter, that have no issues.

This pistol did have one issue of stripping the round off the magazine prior to switching the handguard out as well.

The gunsmith also did not mention the handguard as the culprit either. I am more convinced that they don't have any idea of what is causing these issues, and are just hoping that the issue will go away on its own. Or they are hoping that people don't actually shoot their firearms  .

I'll report back when my pistol arrives. I will most likely attempt it with the aftermarket handguard and the factory one to rule out any possibilities.

[MeatAxe]

I highly doubt the issue is with the aftermarket handguard. The carbine also uses this style of attachment for the handguard, and you don't see any issues with them. In fact, you don't see any issues with the 5.56mm pistols and aftermarket handguards at all. There are many other rifles out there that use the same style of barrel attachment, in .308 for that matter, that have no issues.

This pistol did have one issue of stripping the round off the magazine prior to switching the handguard out as well.

The gunsmith also did not mention the handguard as the culprit either. I am more convinced that they don't have any idea of what is causing these issues, and are just hoping that the issue will go away on its own. Or they are hoping that people don't actually shoot their firearms  .

I'll report back when my pistol arrives. I will most likely attempt it with the aftermarket handguard and the factory one to rule out any possibilities.

Of course, 5.56 is a significantly less powerful cartridge than 7.62x39, so that is very likely a big part of the equation.

You look at the 2S and all the actual military (full auto) versions of the Bren 2, and you see that they all have at least 9 torqued screws and 3 extended plates on the forward part of the receiver (no separate "hand guard") holding the barrel to the receiver. We're not talking about other rifles of different designs. This is the CZ Bren that's been in production as a military rifle for years. You look at pics of the .308 Bren BR and it has even more torque screws holding the front end and barrel together.  No "hand guard" held together by only 4 screws that nobody can decide what the proper torque specs are for them.

When you get your gun back and put the OEM Ms fore end back together on it, be sure to use new screws and nordlock washers torqued to spec since those parts take a beating in the disassembly / reassembly process.

[shineboy2000]

Ah the age old debate, power of 5.56 vs 7.62....

[MeatAxe]

Ah the age old debate, power of 5.56 vs 7.62....

Not much to debate if you've ever shot them, or even looked at ballistics tables (muzzle energy, etc.). Barrier penetration is one that 7.62x39 clearly excels at compared to 5.56.