Author Topic: Bren gas ports?  (Read 1850 times)

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Offline Kenneth

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Bren gas ports?
« on: February 13, 2018, 08:25:38 PM »
I am currently thinking about the Bren gas system. They have a two gas setting but it’s for “normal” and adverse settings. They are both very large.

Anyone have a solution for a suppressed setting?

I see that you can buy new gas regulators from CZ USA now for $80.

Anyone know what sizes they are for the pistol vs the carbine? I believe the carbine is 1.0mm and 1.5mm.

I have been speaking with Black River Tactical and they put set screw gas ports in barrels to tune the gas system on AR’s. I am thinking about if they can do the same with the Bren.


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Offline Kenneth

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Re: Bren gas ports?
« Reply #1 on: February 14, 2018, 03:39:47 PM »
Anyone?


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Offline Laughing Snake

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Re: Bren gas ports?
« Reply #2 on: February 15, 2018, 09:43:26 AM »
I think you're going in the right direction. I don't have my Bren accessible right now but I thought about drilling a third hole and making a third notch to do suppressed. Doing a regulator with a set screw I would think could be manageable.

Offline Kenneth

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Re: Bren gas ports?
« Reply #3 on: February 15, 2018, 09:16:49 PM »
I do not have a Bren either but I don’t know about drilling a third hole. Doesn’t the gas regulator lock in position with a pin?


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Offline Laughing Snake

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Re: Bren gas ports?
« Reply #4 on: February 15, 2018, 11:12:25 PM »
It does. You'd have to make a third cut out for the pin between the two existing ones that would line up with a third gas port.

Offline Czguy91

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Bren gas ports?
« Reply #5 on: March 08, 2018, 01:59:49 PM »
Made an account just to reply to this. Ive done a suppressor port on my bren. The two factory holes are 1.2 and 1.5mm. I drilled a .8mm hole and then notched the front for the pin. Its a bear to get through the chrome but once you do, a carbide bit will get through it. I have 100% reliability so far with a silencerco hybrid. Only issue was no bolt hold open on the last round. This was with direct thread and a .46 end cap. I put the qd muzzle brake on and .308 end cap and will try again today to see if that creates a litte more back pressure. But results firing are extremely good. No overgas and super flat shooting.
« Last Edit: March 08, 2018, 02:10:05 PM by Czguy91 »

Offline Kenneth

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Re: Bren gas ports?
« Reply #6 on: March 08, 2018, 05:09:15 PM »
^^^ oh nice man!

I would like to see how the gas ports hold up with more shooting.



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Offline Czguy91

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Re: Bren gas ports?
« Reply #7 on: March 08, 2018, 11:06:20 PM »
I’ll be sure to show some pics after some use. Just for an update, my suppressor setup did add back pressure, about 70% of the time it would get the bolt to lock back. So i decided to drill it out to .9mm and i think this will be the winner. Also, had my wife shoot it for me on standard and “suppressor” mode. And it has to be at least 5db quitter from the side. It was very noticeable.


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Offline chiba_kun

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Re: Bren gas ports?
« Reply #8 on: May 28, 2018, 02:46:50 PM »
Reviving this thread because it should be talked about more with the new-ish events that have been happening with SCAR owners running suppressed and FNs customer service shutting people down. I can elaborate on that for whoever isn’t aware.

I just got a “Bren pistol” gas plug for my carbine. As listed in the CZ website, the carbine gas plug holes are 1.4mm and 1.7mm. The 11” Bren (pistol) gas port as listed on CZs website is 1.2mm.
I haven’t had a chance to go shooting yet, but I would imagine that if czguy91 is having the issue of a slight short cycle (not cycling far enough back to hold open after the last shot) with a .8mm port, using the 1.2mm port will work nicely. The bonus is that, in the event that it is still a bit too much gas and with the knowledge that a .8mm hole isn’t quite enough, the 11” barrel plug only has one setting, so a secondary 1mm hole can be added in the same factory location as the carbines second setting.

I’m planning on going shooting in a few days, so I’ll try to update.
« Last Edit: May 28, 2018, 04:04:15 PM by chiba_kun, Reason: Updated gas plug hole sizes »

Offline Czguy91

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Re: Bren gas ports?
« Reply #9 on: May 28, 2018, 03:07:24 PM »
Reviving this thread because it should be talked about more with the new-ish events that have been happening with SCAR owners running suppressed and FNs customer service shutting people down. I can elaborate on that for whoever isn’t aware.

I just got a “Bren pistol” gas plug for my carbine. As listed in the CZ website, the carbine gas plug holes are 1.2mm and 1.5mm. The 11” Bren (pistol) gas port as listed on CZs website is 1mm.
I haven’t had a chance to go shooting yet, but I would imagine that if czguy91 is having the issue of a slight short cycle (not cycling far enough back to hold open after the last shot) with a .8mm port, using the 1mm port will work nicely. The bonus is that, in the event that it is still a bit too much gas and with the knowledge that a .8mm hole isn’t quite enough, the 11” barrel plug only has one setting, so a secondary .9mm hole can be added in the same factory location as the carbines second setting.

I’m planning on going shooting in a few days, so I’ll try to update.
Good to know man. This would make it easier for people that arent quite as handy. I`m still shooting on suppressor setting and havent had any erosion. Its surprising how significant .3mm can make in sound and recoil.

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Offline Kenneth

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Re: Bren gas ports?
« Reply #10 on: May 28, 2018, 06:58:20 PM »
Thanks for the update. I have spoken to multiple people and no one is really interested in tuning the Bren.

That’s why I would like to see what port size and how the erosion acts.

A Bren pistol that has a SB brace and a suppressor setting is what I’m looking for.




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Offline chiba_kun

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Re: Bren gas ports?
« Reply #11 on: May 28, 2018, 07:48:33 PM »
Erosion should never be an issue, unless you somehow find some corrosive 5.56 and never clean your rifle.

Also, I should probably include that I’m running a 13.7” barrel with a pinned/welded muzzle device on my carbine, not the full 16.2”

Offline Kenneth

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Re: Bren gas ports?
« Reply #12 on: May 28, 2018, 07:51:56 PM »
I know multiple people have shown their gas ports and they look terrible for the amount of rounds they have fired.

It was like the metal was not treated correctly or something.


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Offline chiba_kun

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Re: Bren gas ports?
« Reply #13 on: May 30, 2018, 07:57:04 AM »
I know multiple people have shown their gas ports and they look terrible for the amount of rounds they have fired.

It was like the metal was not treated correctly or something.


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That’s alarming.

Ok so a quick update...I had my machinist measure the gas ports on the carbine gas plug and he said that the gas port sizes are 1.15mm and 1.3mm. So as I expected, the info on the CZ site isn’t correct.
On the 11”bbl gas plug the single port size is also 1.15mm.
 He didn’t get a chance to add a secondary (suppressed) hole for me yet, so I won’t get to go shooting today, but I’ve asked that the secondary hole be set at .8mm with the info from CZguy91  that the increased backpressure with a can on should help cycle the bolt carrier. I can always open the port up slightly if .8mm doesn’t get lock back after the last round, but I’m hoping that my shortened bbl length will play a part.

Offline Kenneth

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Re: Bren gas ports?
« Reply #14 on: May 30, 2018, 09:41:22 PM »
I know multiple people have shown their gas ports and they look terrible for the amount of rounds they have fired.

It was like the metal was not treated correctly or something.


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That’s alarming.

Ok so a quick update...I had my machinist measure the gas ports on the carbine gas plug and he said that the gas port sizes are 1.15mm and 1.3mm. So as I expected, the info on the CZ site isn’t correct.
On the 11”bbl gas plug the single port size is also 1.15mm.
 He didn’t get a chance to add a secondary (suppressed) hole for me yet, so I won’t get to go shooting today, but I’ve asked that the secondary hole be set at .8mm with the info from CZguy91  that the increased backpressure with a can on should help cycle the bolt carrier. I can always open the port up slightly if .8mm doesn’t get lock back after the last round, but I’m hoping that my shortened bbl length will play a part.


Thank both of you for this. This has been causing me to hold off on a Bren and just thinking about an AR pistol with adjustable gas.


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