Suppressed gas key hole size on the Bren 1 & 2

[Mr_5lade]

Hey all, I’m going to rework the gas key on the 11” 805 to have a suppressed setting and also going to drill out the “off” setting on the 8” Bren 2 5.56. Is there a consensus of drill bit size? It looks as though the “regular” setting hole size for the 805 is 1.2mm - is this correct? I’m not sure on the 2... Any input would be appreciated. Thanks 

[Aries144]

Pretty sure you're the first and this is going to be a trial and error thing. Start small, test, open it up a little, test, etc. If you can't shoot nearby to your drilling tools, you might try precision drilling a starter hole smaller than you think is needed, then using a hand tool at the range to open up the hole until desired function is achieved.

If you can lay hands on a high speed camera (there are some cheap enough to use for diagnostics like this), you can compare the bolt velocity when the rifle is unsuppressed/normal gas setting to your suppressed/suppressor gas setting and stop enlarging the hole when comparable timing is achieved.

[beanz2]

I’m not of any authority, but I recall a guy on arf.com saying his aim is 0.8 mm for the suppresses setting.

His concern is surface treatment of the metal after he drills it as the drill leaves unprotected metal behind.

Hope someone can shed a light here...


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[Aries144]

If you can find a company that nitrides steel parts, ask them what they think about re nitriding an already nitrided part after drilling.

The gas port on the Bren 2 barrels is drilled pretty close to the chamber compared to other designs, which means higher pressures and temperatures from those gases. Retreating the part after drilling wouldn't be a bad idea to reduce erosion, if re nitriding is possible.

[Mr_5lade]

Great info you guys I appreciate it. I do have an AK shop here that I believe nitrates. I will do a write up once I’m done with this project 👍 The suppressor is going to be a Dead Air Wolverine. I may also try the Silenserco Omega 300 on the gen one to compare back pressure.

[Aries144]

Don't forget to post back when you get it done! I'm particularly interested in what the nitride shop says about re nitriding.

[Mr_5lade]

Okay... got the hole drilled finally. I don’t know if any of you have drilled through hardened steal that happens to have a curved surface, with a micro 1/32” drill bit, but yeah... Make sure you have plenty of bits on hand and plenty of Zen... I was almost through on my first run and had a bit break clean off in the hole. I couldn’t get it out so I used a Dremel cone bit and cleared the area to about half way down and drilled from there. I used QualTech 1/32” Cobalt Jobber drill bits. These bits were reasonably priced off Amazon. Maybe someone who knows more about machining can chime in. I did find bits that approached $100.00ea but couldn’t justify that amount - especially with the high chances off bit breaking. The oil I used was Oatey Dark Thread Cutting Oil.

The Bren 2 is off getting a cerakote job done right now and I have an adapter from Dead Air on order. I’ll be running the Wolverine can.

I’ll keep y’all updated as soon as things happen




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[Mr_5lade]

I wanted to add I don’t have the Bren 1 drilled out yet.


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[Aries144]

Thanks for the update!

I wish you had mentioned issues drilling the curved surface. There's a similar problem with drilling a curved surface and walking bits when replacing AK barrels. The trick is to use an end mill bit to make a flat spot and go nice and slow with the drill bit after that.

[rc4ch]

I wanted to add I don’t have the Bren 1 drilled out yet.


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Any updates on this? Hows the gas to the face?

[gasxsnake]

I just wonder is it necessary? Isn't most can just doing fine on Bren2?

[Magsz]

I just wonder is it necessary? Isn't most can just doing fine on Bren2?

Depends on what you mean by "fine".

I have a 9 inch Bren 2 that is horribly over gassed.  The YHM cans are known to be relatively high back pressure.  I'm not sure how my Resonator K will be as its in jail but if its anything like its 5.56 little brother, my bren with this can will probably eat itself alive.  This gun will definitively need a suppressor setting on the gas plug to reduce bolt velocity.

[gasxsnake]

I just wonder is it necessary? Isn't most can just doing fine on Bren2?

Depends on what you mean by "fine".

I have a 9 inch Bren 2 that is horribly over gassed.  The YHM cans are known to be relatively high back pressure.  I'm not sure how my Resonator K will be as its in jail but if its anything like its 5.56 little brother, my bren with this can will probably eat itself alive.  This gun will definitively need a suppressor setting on the gas plug to reduce bolt velocity.

Cool, hope you get good results!

[Mr_5lade]

I wanted to add I don’t have the Bren 1 drilled out yet.


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Any updates on this? Hows the gas to the face?

I haven’t been able to get out to the range since the pandemic started. I’ll keep you updated though as soon as I find out


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[EFR]

What about trying the gas tube for the 11" 5.56?  You would not have your third customized suppressor setting, but the first two ports would be smaller.  They were available on the CZ website.  Although not cheap ($68 IIRC), they may be a solution to overgassed suppressed firing.