Author Topic: Bren Gas tube wear  (Read 1129 times)

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Offline fakahatchee

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Re: Bren Gas tube wear
« Reply #30 on: January 29, 2018, 04:14:21 PM »
 The tube wall is .090 thick. With the erosion I've got after 1000 rounds it mite make it to 3 or 4 thousand rounds. I got mine from Bud's in Nov. 2017 when they first reduced the price to 1360.00. I sure wish someone else will measure the orifice in the barrel itself, it's easy just remove the gas tube, there is a hole in the bottom of the gas block that lines up with the barrel orifice, in mine a 7/64, .109, drill bit will easily go in so the hole is probably closer to .110- .112.     
If you look at all the pictures of the bad erosion you can see the larger diameter of the wear. In the picture from 2015 with 10,000 rounds the wear is just around the orifice itself. If the problem isn't with the gas tube maybe they sent some barrels out with  the barrel orifice too large.

     Just got off the phone with CZ Warr. again. Asked him about barrel orifice size and if these were US barrels, he didn't know the answer of either. Just kept repeating that this was a wear item and amount of wear depends on what ammo, atmospheric conditions, cleaning regiment. There not going to own up to anything. I told him about this forum and AK Files and to take a look.   
« Last Edit: January 29, 2018, 04:51:53 PM by fakahatchee »

Offline armoredman

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Re: Bren Gas tube wear
« Reply #31 on: January 29, 2018, 09:33:37 PM »
The BREN barrels are made in the Czech Republic, per CZ-USA - who did you speak to?. I see another brand new member pops up with his picture of an eroded barrel - you guys know each other?

Offline MikeinCA

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Re: Bren Gas tube wear
« Reply #32 on: January 29, 2018, 09:47:02 PM »
If you shine a flashlight into the gas block there is a visible step in the hole diameter of the gas orifice (See photo).  The hole in the gas block is approximately 11/64".  But the hole drilled into the barrel is a smaller approx 3/32" (i.e. 6/64").

The FN SCAR has a similar step in the hole diameter from the barrel to the gas block.  However, the FN SCAR uses a removable, gas jet orifice (with various hole sizes) which threads into the larger diameter hole of the gas block to adjust the amount of gas tapped off.  While the CZ 805 gas system appears to use the 2 different sized holes in the gas tube/gas plug as its way of adjusting the amount of gas tapped off to the gas piston.


Offline thehun

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Re: Bren Gas tube wear
« Reply #33 on: January 30, 2018, 10:36:02 AM »
Wonder if one could make a gas block plug like the SCAR barrels have?  O0

I think the erosion on the gas plug happens because the barrel orifice is too large...and all the crud and high pressures are hitting against the gas plug.

Looking at that picture (and confirming on my gun)...I dont see a way around the accelerated erosion...I don't have a way to measure my gas hole size...but maybe new production barrels have a larger hole...mine is an early 2016 FDE gun.

Offline GeeMan

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Re: Bren Gas tube wear
« Reply #34 on: January 31, 2018, 11:57:52 AM »
Interesting to see this topic come back around regarding some newer observations of this phenomenon...  the 2015 post was mine, back when the same thoughts were going through my mind about how much wear was 'too much'...  obviously, the difference I'm seeing is apparently a much more accelerated wearing process than what I personally have experienced...  the 2015 post was based around my 805 pistol (original PS1 purchased in 2014), as the carbines were not being sold yet in the US...  I later did buy an 805 carbine the week they were released, which became my go-to fight rifle that I have used in all of my live fire training since then...  it now has 19k+ rounds out of the pipe and I have had ZERO issues with it...  no malfs, no broken parts, no loss of inherent accuracy, etc., and I am NOT gentle with my rifle...  these weapons are tanks...  to try and answer a couple of questions now that will likely be asked: the gas block port hole and barrel gas port hole in my rifle is dimensionally the same as what is described above in the post...  yes, the wear on my gas tube at the 'standard' setting hole increased slightly, but nothing like in the photos shown in this thread...  no, I have NEVER had any debris jettisoned out of the gas vent area and strike me that I've ever noticed...  only the usual carbon film buildup around the outside of the gas tube and on the front of the sling loop plate/upper receiver...  I am no scientist and so can't offer any theories based on knowledge of metallurgy, but the only thing that comes to mind with all other things being equal is that a different/weaker/softer metal was used for the gas tube that allows it to erode at a faster rate than the earlier versions...  this is speculation of course, but without some other mitigating circumstance being involved (out of spec mfg., corrosive ammo, etc.) I don't have anything else to offer...  for further review, here is a (FB) link that I hope works with various photos of my carbine at the approx. 19k round mark...

https://www.facebook.com/groups/1889292077962564/permalink/2402395899985510/


Offline thehun

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Re: Bren Gas tube wear
« Reply #35 on: January 31, 2018, 03:21:31 PM »
That is amazing at 19K...your gas plug does appear to be Czech...my carbine does not have the 8 stamping...maybe the gas plug are use made out of softer metal/chrome plating.

Offline MikeinCA

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Re: Bren Gas tube wear
« Reply #36 on: January 31, 2018, 05:40:30 PM »
The gas tube which I had posted the picture showing the erosion also has an "8" stamped on the flat.

I purchased my FDE CZ 805 in late 2016.  The serial number range of mine is C0214xx

Offline Wusteadler

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Re: Bren Gas tube wear
« Reply #37 on: January 31, 2018, 05:45:25 PM »
Well, gave CZ another chance to replace parts on mine, but the warranty dept informed me that they have NO replacement barrels, and the gas tube is normal. So I should have a check by mid February. Sad deal, but it is what it is.

Offline thehun

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Re: Bren Gas tube wear
« Reply #38 on: February 02, 2018, 10:50:05 AM »
https://www.ar15.com/forums/armory/Consensus-on-CZ-Bren/2-460988/&page=23

Take a look at the above link.

It appears that the chrome plating erodes...but the actual metal for the gas plug is holding just fine...I am not worried about this erosion.

Offline DDNC

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Re: Bren Gas tube wear
« Reply #39 on: February 03, 2018, 07:15:12 PM »
https://www.ar15.com/forums/armory/Consensus-on-CZ-Bren/2-460988/&page=23

Take a look at the above link.

It appears that the chrome plating erodes...but the actual metal for the gas plug is holding just fine...I am not worried about this erosion.
I agree. In an earlier post I surmised it was just the chrome plating flaking off. The GB orfice is twice the size of the valve orfice so the surface is being blasted by high temp/ high pressure gas which then is forced into the smaller port. It’s a plating and it is possible for it to flake.
The valve orfice is unchanged in size. Therefore, until that changes it’s not an issue.
« Last Edit: February 03, 2018, 07:21:42 PM by DDNC »