Author Topic: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:  (Read 1153 times)

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Offline Magsz

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Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« on: September 03, 2020, 06:17:29 PM »
Guys,

I'm trying really hard not to beat a dead horse.  This post is only to present pictures of what a bren 2 with 5100 rounds on it looks like.

2019 Production 9 inch 7.62X39 Bren 2 MS.

HBI handguard added at an unknown round count. Probably the 2500 round mark.  The gun exhibited failures prior to but at the time, I attributed it to the clear magazines that I was running which were developing cracks.

My only real observations are the following:

The firing pin retaining pin "clip" "clamp" "retaining hook" is getting beat to crap by the trigger which is contacting it.  I have yet to have any failures to fire and I believe this peening will stop eventually or not get any worse so i'm not overly concerned about this.  I have no clue how this progressed as I really only shoot and add lube.

The bolt lugs have some minor deformation from unlocking.  Nothing catastrophic.  No evidence of cracks or serious deformation that would inhibit function.

My extractor claw is rounding off on the underside.  Like a dolt I forgot to take a picture of this.

My extractor barely moves with the current spring and insert.  Cleaning does not change its range of motion.

My "normal" gas port size after 5100 rounds on the plug is 1.69mm's measured with crappy chinese calipers.  I triple checked this.

My recoil spring retainer is bending.

The finish flaked off of the rear of my recoil rod and was found in the action as little silver flakes.

Here are the pics:











« Last Edit: September 04, 2020, 09:16:08 PM by Wobbly, Reason: Mods set photo width to 500 »

Offline sneakyhenry

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #1 on: September 03, 2020, 06:38:52 PM »
Have you ran it suppressed at all? Is this a Ms or s model?

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #2 on: September 03, 2020, 06:46:14 PM »
Have you ran it suppressed at all? Is this a Ms or s model?

I ran it suppressed for about two hundred rounds.  It shot like pure crap with cases literally ejecting forward.  It was also completely unreliable with numerous malfunctions each magazine.

Sandman K and a YHM Resonator K, both on keymo mounts with a dead air brake.

Offline czkyle1776

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #3 on: September 03, 2020, 07:51:14 PM »
Do you have a borescope? I'd be interested to see what the gas port looks like.

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #4 on: September 03, 2020, 08:23:21 PM »
Do you have a borescope? I'd be interested to see what the gas port looks like.

I do not, sorry bud!

Offline sneakyhenry

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #5 on: September 04, 2020, 11:32:54 AM »
Did you have any issues running it unsuppressed, just shooting it regularly?

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #6 on: September 04, 2020, 01:52:47 PM »
Yes.

So many failures to eject that I stopped counting.  The gun has already gone back to CZ once which did not fix the issue.

Offline MeatAxe

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #7 on: September 04, 2020, 02:10:12 PM »
Yes.

So many failures to eject that I stopped counting.  The gun has already gone back to CZ once which did not fix the issue.


From what I’ve seen here, yours is not the only 7.62 Bren 2 that’s been sent back to CZ USA for repairs and came back with the same malfunctions.

This is the crux of the matter: the weapon is obviously malfunctioning, was sent back for repairs, returned to you and still malfunctions. Overgassed as it obviously is, the likely culprit is an over large gas port. The only real solution is a brand new barrel, properly ported. Unfortunately, CZ USA has no replacement parts at all, so they try to blame “shoddy ammunition” which is a load of bs. These are (supposedly) military rifles, so they ought to be able to handle a wide array of ammunition, most of it former com bloc steel cased (dirty) ammunition. It’s got an “adverse conditions” setting on the gas regulator for chissakes - which is not the issue, it’s just the opposite - too much gas.

So I think CZ USA is just obfuscating with this “shoddy Ammo” excuse because they’ve obviously dropped the ball in terms of parts, service and in this instance, quality control.
« Last Edit: September 04, 2020, 02:15:39 PM by MeatAxe »

Offline MeatAxe

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #8 on: September 04, 2020, 02:41:56 PM »
Do you have a borescope? I'd be interested to see what the gas port looks like.

I do not, sorry bud!


Lyman sells a decent borescope / digital camera for @ $250 that has become indispensable for me. There’s really no other way to get a good look at the inside of your bore,

FWIW I took a look at the gas port on my 11” 7,62 Bren Ms from inside the bore. While there’s no way for me to gauge the size of the gas port from the inside, I could see that it was more or less centered in one of the lands and spanned about 3/4 of the width of said land. No discernible port erosion after @ 1,000 rounds.

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #9 on: September 14, 2020, 06:53:26 PM »
5300 rounds down the tube.  Another 200 today.

I lost count of the failures to eject after 5.

Video will be up later.

Offline dkozy

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #10 on: September 14, 2020, 10:25:06 PM »
5300 rounds down the tube.  Another 200 today.

I lost count of the failures to eject after 5.

Video will be up later.

You state that you don't clean the rifle just lube and shoot. Have you tried cleaning it really good? Also, if you field strip the rifle and take out the recoil spring so that the only thing in the rifle is the BCG. Does the BCG slide in and out of battery with no resistance at all. I'm talking about NO resistance, just slides in like butter? Do you have numbered drill bits? Not standard bits but drill bits that are sized like 60-20? If so try to find a drill bit that fits nice and tight in your number one hole and ill see how it compares to my fairly new rifle.

Offline MeatAxe

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #11 on: September 15, 2020, 06:59:49 PM »
Guys,

I'm trying really hard not to beat a dead horse.  This post is only to present pictures of what a bren 2 with 5100 rounds on it looks like.

2019 Production 9 inch 7.62X39 Bren 2 MS.

HBI handguard added at an unknown round count. Probably the 2500 round mark.  The gun exhibited failures prior to but at the time, I attributed it to the clear magazines that I was running which were developing cracks.

My only real observations are the following:

The firing pin retaining pin "clip" "clamp" "retaining hook" is getting beat to crap by the trigger which is contacting it.  I have yet to have any failures to fire and I believe this peening will stop eventually or not get any worse so i'm not overly concerned about this.  I have no clue how this progressed as I really only shoot and add lube.

The bolt lugs have some minor deformation from unlocking.  Nothing catastrophic.  No evidence of cracks or serious deformation that would inhibit function.

My extractor claw is rounding off on the underside.  Like a dolt I forgot to take a picture of this.

My extractor barely moves with the current spring and insert.  Cleaning does not change its range of motion.

My "normal" gas port size after 5100 rounds on the plug is 1.69mm's measured with crappy chinese calipers.  I triple checked this.

My recoil spring retainer is bending.

The finish flaked off of the rear of my recoil rod and was found in the action as little silver flakes.

Here are the pics:












I'm no expert, but from the pics it's pretty obvious that your gun's internals have taken a beating from overpassing. Function is probably just getting worse as wear increases.

Looking at the gas plug, from the scorch marks, it appears that some of the exhaust gas was bypassing the #1 hole and getting into the #2 “adverse conditions” hole, making matters worse. So my guess continues to be that the gas port on the barrel was drilled too big at the factory.

You might try drilling a tiny hole at the "0" position on the gas plug (like MAC did) and progressively enlarge it to "tune" for optimum gas modulation.

Are you sending this gun to MAC for evaluation?
« Last Edit: September 16, 2020, 06:03:07 AM by MeatAxe »

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #12 on: September 16, 2020, 01:54:44 AM »
5300 rounds down the tube.  Another 200 today.

I lost count of the failures to eject after 5.

Video will be up later.

You state that you don't clean the rifle just lube and shoot. Have you tried cleaning it really good? Also, if you field strip the rifle and take out the recoil spring so that the only thing in the rifle is the BCG. Does the BCG slide in and out of battery with no resistance at all. I'm talking about NO resistance, just slides in like butter? Do you have numbered drill bits? Not standard bits but drill bits that are sized like 60-20? If so try to find a drill bit that fits nice and tight in your number one hole and ill see how it compares to my fairly new rifle.

As per CZ, the gas port and piston were cleaned during its trip to their facility.  I also cleaned the gun extremely well after its return from CZ.

The gun was an absolute failure, even after cleaning.  To be honest with you, my bolt wasn't really all that dirty.  The gun had gunk in it but nothing that should inhibit function during the extraction and ejection cycle.  As noted, my extractor does not move freely and has a huge amount of tension on it.  No clue if this is contributing to the failures but I would suspect its part of the issue along with the over gassing present.

Offline Aries144

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #13 on: September 16, 2020, 02:15:42 PM »
The only reason the extractor moves at all is to allow it to slip over the rim of a cartridge during feeding. You don't want it to move during extraction or ejection. If it did, you'd get a failure to extract or failure to eject, depending on when it slips off the cartridge rim.

Offline Magsz

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Re: Photos: 7.62X39 9 Inch Bren 2 5100 Rounds Down The Tube:
« Reply #14 on: September 16, 2020, 07:07:04 PM »
The only reason the extractor moves at all is to allow it to slip over the rim of a cartridge during feeding. You don't want it to move during extraction or ejection. If it did, you'd get a failure to extract or failure to eject, depending on when it slips off the cartridge rim.

Very true, however, if the extractor is so stiff that its not fully grasping the cartridge rim, that could cause an issue as well.

I don't have camera's good enough to capture what's happening in the ejection port.