Author Topic: 7.62x39 fix??  (Read 6441 times)

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Offline Bret

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Re: 7.62x39 fix??
« Reply #30 on: October 08, 2022, 09:41:06 PM »
I shot my Bren 2Ms today and had pretty good results with the new gas valve.  150rds of Tula 122gr FMJ copper jacket and 45rds of Golden Tiger 124gr FMJ were put through the rifle.  It's setup to use 7.62x39 AR15 magazines.  I used a 30rd D&H, a 20rd ASC and a RZE Unimag.  Immediately, I could tell that the cases were ejecting with less velocity.  Ejection was generally from 1:30 to 2:00 and the cases went only about 4'.  Slo-mo video showed that the cases were actually deflecting off of the case deflector and then going to 1:30 to 2:00.  I did have an issue when using the RZE Unimag.  Both times I attempted to shoot 25rds though it, the BCG locked back when the 3rd cartridge was feeding.  It turns out that the cartridges in the magazine were nose diving and the base of the top cartridge was stopping the bolt carrier in its tracks.  It's interesting that this happened on the 3rd cartridge each time and didn't repeat while shooting further through the magazine.  Though I have had great success using the Unimags in other 7.62x39 rifles, I can't blame the CZ Bren which wasn't actually even designed to use 7.62x39 AR15 magazines.  Rather, it was designed to use their proprietary continuous curve 7.62x39 magazines.  Given that the problem didn't occur with the D&H nor ASC magazines, I'm just going to avoid using the Unimags in this rifle.  I'll obviously put some more ammunition through this rifle before I'm confident, but I feel like it's on the right path.  Below is a picture of the jam when using the Unimag.  The arrow points to the base of the cartridge that caused the stoppage.


Offline Bret

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Re: 7.62x39 fix??
« Reply #31 on: October 24, 2022, 09:33:49 AM »
Yesterday I fired 20rds of Tula 122gr FMJ copper jacket using an ASC 20rd magazine and 30rds more of the same using a D&H 30rd magazine.  The rifle functioned 100% with ejection to about 1:00.  Spent cases are hitting off of the case deflector and going back forward.  A few hit my left hand as it was gripping the handguard.  I think the over gassing issue is solved, but there's still an issue with the ejection direction.  I understand that the case deflector is supposed to deflect spent cases that are heading too far rearward, but they're hitting it square and going back forward.  A different shape to the case deflector would help, but I'm still left thinking that there is some sort of ejection timing issue. 

Offline America_First

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Re: 7.62x39 fix??
« Reply #32 on: October 25, 2022, 05:31:13 PM »
Yesterday I fired 20rds of Tula 122gr FMJ copper jacket using an ASC 20rd magazine and 30rds more of the same using a D&H 30rd magazine.  The rifle functioned 100% with ejection to about 1:00.  Spent cases are hitting off of the case deflector and going back forward.  A few hit my left hand as it was gripping the handguard.  I think the over gassing issue is solved, but there's still an issue with the ejection direction.  I understand that the case deflector is supposed to deflect spent cases that are heading too far rearward, but they're hitting it square and going back forward.  A different shape to the case deflector would help, but I'm still left thinking that there is some sort of ejection timing issue. 

Quick question, are you using the HBI piston spring? 

Offline Bret

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Re: 7.62x39 fix??
« Reply #33 on: October 25, 2022, 06:28:37 PM »
Quick question, are you using the HBI piston spring?
Yes.  Why do you ask?

Offline America_First

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Re: 7.62x39 fix??
« Reply #34 on: October 26, 2022, 04:19:42 PM »
Then there's likely another issue causing erratic or delayed ejection.  Have you cleaned the ejector spring channel in the bolt? I noticed some images of the extractor removed, which is what we originally thought the issue was back in 2020. 

If CZ-USA offered spare bolts, this would be such an easy fix.  That's really all we want, is a SPARE BOLT!  How difficult could this be for a manufacture like CZ-UB?
« Last Edit: October 26, 2022, 04:29:12 PM by America_First »

Offline Bret

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Re: 7.62x39 fix??
« Reply #35 on: October 26, 2022, 04:38:41 PM »
I removed the extractor from the bolt, but not the ejector.  I'll give it a look.

Offline MeatAxe

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Re: 7.62x39 fix??
« Reply #36 on: October 26, 2022, 07:27:57 PM »
I removed the extractor from the bolt, but not the ejector.  I'll give it a look.

Whatever you do, don’t lose any of the ejector and extractor parts. CZ Bren 2 parts are as rare as hens’ teeth — especially such critical wear / replacement parts. I’ve been trying to accumulate such bolt parts for years (literally) so I’d have replacements in case any of those parts were to spring into outer space while disassembling the bolt.

There’s really no excuse for CZ not supporting the Bren 2. And now we’re hearing that CZ plans to stop importing the Bren 2 to the US, at least temporarily? Ridiculous.
« Last Edit: October 26, 2022, 07:32:29 PM by MeatAxe »

Offline mig1nc

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Re: 7.62x39 fix??
« Reply #37 on: October 27, 2022, 07:06:13 AM »
I removed the extractor from the bolt, but not the ejector.  I'll give it a look.

Whatever you do, don’t lose any of the ejector and extractor parts. CZ Bren 2 parts are as rare as hens’ teeth — especially such critical wear / replacement parts. I’ve been trying to accumulate such bolt parts for years (literally) so I’d have replacements in case any of those parts were to spring into outer space while disassembling the bolt.

There’s really no excuse for CZ not supporting the Bren 2. And now we’re hearing that CZ plans to stop importing the Bren 2 to the US, at least temporarily? Ridiculous.
Do you have a source for that info?


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Offline America_First

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Re: 7.62x39 fix??
« Reply #38 on: October 27, 2022, 12:52:48 PM »
I removed the extractor from the bolt, but not the ejector.  I'll give it a look.

Whatever you do, don’t lose any of the ejector and extractor parts. CZ Bren 2 parts are as rare as hens’ teeth — especially such critical wear / replacement parts. I’ve been trying to accumulate such bolt parts for years (literally) so I’d have replacements in case any of those parts were to spring into outer space while disassembling the bolt.

There’s really no excuse for CZ not supporting the Bren 2. And now we’re hearing that CZ plans to stop importing the Bren 2 to the US, at least temporarily? Ridiculous.

100% AGREE with every word said here. 

HBI created a video that went through the entire disassembly process, which was never released publicly.  The difficulty isn't in the disassembly, it's in the fact that if you lose or damage any component, there is no spare parts to replace them with.  Literally, an ejector spring that costs CZ-UB $0.10 cents or less to manufacture is non-existent.  There is no excuse. 

Offline MeatAxe

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Re: 7.62x39 fix??
« Reply #39 on: October 27, 2022, 02:33:17 PM »
I removed the extractor from the bolt, but not the ejector.  I'll give it a look.

Whatever you do, don’t lose any of the ejector and extractor parts. CZ Bren 2 parts are as rare as hens’ teeth — especially such critical wear / replacement parts. I’ve been trying to accumulate such bolt parts for years (literally) so I’d have replacements in case any of those parts were to spring into outer space while disassembling the bolt.

There’s really no excuse for CZ not supporting the Bren 2. And now we’re hearing that CZ plans to stop importing the Bren 2 to the US, at least temporarily? Ridiculous.

100% AGREE with every word said here. 

HBI created a video that went through the entire disassembly process, which was never released publicly.  The difficulty isn't in the disassembly, it's in the fact that if you lose or damage any component, there is no spare parts to replace them with.  Literally, an ejector spring that costs CZ-UB $0.10 cents or less to manufacture is non-existent.  There is no excuse.


Yeah, right now my Bren 2 is functional and not jamming, but it just sits in the safe collecting dust. I don’t dare shoot it or disassemble the small parts because if anything breaks or gets lost, my Bren 2 is just an oversized paper weight — until such time (if ever) that CZ deigns to support these guns.

Offline MeatAxe

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Re: 7.62x39 fix??
« Reply #40 on: October 27, 2022, 03:11:57 PM »

Do you have a source for that info?



They’ve been talking about it on ARFCOM, apparently sources from former CZ USA employees getting laid off (not a good sign, especially if Colt is taking over). Also was on a recent Patreon-only video on MAC where he mentioned that rumor — along with discouraging people from buying the Bren 2, with a lot of justification considering the cost, problems, lack of support and lackluster accuracy.
« Last Edit: October 28, 2022, 10:17:34 AM by Wobbly »

Offline Bret

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Re: 7.62x39 fix??
« Reply #41 on: November 27, 2022, 04:21:52 PM »
I took my 11" Bren2 Ms out again today and put 90rds through it.  Ejection is weird.  Half of the spent cases go to about 12:30 and the other half go to about 2:30.  There was one stovepipe on a spent case where the following cartridge fed into the chamber.  My guess is that the spent case hit off the rear of the ejection port, bounced forward and was caught by the bolt carrier going forward.  This is so frustrating because the ergonomics and light weight of this rifle make it feel great in my hands.


 
I removed the ejector.  Its channel appears clean.  The only oddity that I found was a little ring that was around the part that the arrow points to.  I can't really tell if it's metal or rubber.


« Last Edit: November 30, 2022, 06:19:01 PM by Bret »

Offline MeatAxe

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Re: 7.62x39 fix??
« Reply #42 on: November 28, 2022, 07:46:30 AM »
I took my 11" Bren2 Ms out again today and put 90rds through it.  Ejection is weird.  Half of the spent cases go to about 12:30 and the other half go to about 2:30.  There was one stovepipe on a spent case where the following cartridge fed into the chamber.  My guess is that the spent case hit off the rear of the ejection port, bounced forward and was caught by the bolt carrier going forward.  This is so frustrating because the ergonomics and light weight of this rifle make it feel great in my hands.


 
I removed the ejector.  Its channel appears clean.  The only oddity that I found was a little ring that was around the part that the arrow points to.  I can't really tell if it's metal or rubber.




That is indeed odd — there is no “O” ring or anything similar shown with the ejector on the official Bren 2 parts schematic. I don’t recall seeing one on the couple of spare ejectors I’ve been able to (sporadically) acquire from the CZ USA Webstore.

Does it eject / cycle better without the O ring?
« Last Edit: November 28, 2022, 07:50:37 AM by MeatAxe »

Offline Bret

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Re: 7.62x39 fix??
« Reply #43 on: November 28, 2022, 04:45:49 PM »
It's still taken apart, so I don't know.  I can't figure out why they made the spring so long.

 

anything