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Posted: 4/5/2016 8:02:27 PM EDT
Normally I would not have posted this, I have my pride after all, but I wanted to send out a little warning in this area for ANYONE looking at the BCM Kino 12.5" upper receiver group.
Initially i was putting together a plan for an SBR build that was going to be shot about 250 rounds a week and was going to be ran suppressed almost exclusively. I chose the aforementioned BCM configuration. That wasn't a mistake. The upper is definitely quality and holy crap the barrel shoots well with 77 grain SMKs. The MISTAKE was using an SLR gas block to mitigate the overgas.
Yeah...so I learned a few things.
1. SLR Gas block screws LOCK UP when you run 500 rounds through a gun without twisting the screw and breaking the carbon loose. I've heated the sucker up, tried using pliers to spin the screw (2mm ball driver stripped off like nothing), and using every carbon cleaner I know of. The only reason I actually wanted to close off the gas was to clean my bore, and SLR recommends closing off the gas port before using bore cleaners. At this point if I ruin it then I ruin it and have an excuse to buy a new one.
2. Taking FSB pins out of the same barrel a half dozen times I'm just two weeks of shooting for standard maininence is ridiculous and you will feel stupid every time. I've officially just said NO MORE FSB. So what if I have big channels visible in my barrel from now on. Better than taking an FSB off every time your gas block locks up.
3. Before anyone suggests a Govnah, I don't even know if I want to try.

I feel line it's absolutely my fault for not having the foresight to see the obvious issue, but I learned the hard way so you don't have to.
Link Posted: 4/5/2016 8:14:09 PM EDT
Link Posted: 4/5/2016 8:28:46 PM EDT
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Quoted:
You could have left the stock gas block on and it would run 100%
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Shhhhhhhhh.
I know that. But in my way of thinking it would have been overgassed running suppressed and I NEEDED to be able to mitigate that because of reasons.
Link Posted: 4/5/2016 8:32:43 PM EDT
Link Posted: 4/5/2016 8:39:35 PM EDT
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Quoted:



I won't tell you my suppressed BCM 12.5 is going strong at about 3K rounds and no malfunctions then.

IMHO, over gassed, as a term, is getting tossed around so much that its actually creating problems. Your case in point. There are some 10.5" guns that are over gassed. And there are some >10.5" guns that maybe have the gas ports drilled a little loose, to run all kinds of cheap, shitty ammo. But I wouldn't try to fix the gas "problem" without making sure its actually happening first.
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Quoted:
Quoted:
Quoted:
You could have left the stock gas block on and it would run 100%


Shhhhhhhhh.
I know that. But in my way of thinking it would have been overgassed running suppressed and I NEEDED to be able to mitigate that because of reasons.



I won't tell you my suppressed BCM 12.5 is going strong at about 3K rounds and no malfunctions then.

IMHO, over gassed, as a term, is getting tossed around so much that its actually creating problems. Your case in point. There are some 10.5" guns that are over gassed. And there are some >10.5" guns that maybe have the gas ports drilled a little loose, to run all kinds of cheap, shitty ammo. But I wouldn't try to fix the gas "problem" without making sure its actually happening first.


I have run several other suppressed SBR rifles, while not BCM but generally the same that have an obvious amount of extra gas coming into the receiver as well as faster cyclic rate. My notion of adjustable gas was to bring the cyclic rate of the rifle back to the "normal" point by my own perceptions. Basically where it will run reliably but isn't getting more gas than is necessary to function the rifle for long periods of time.
Link Posted: 4/5/2016 8:40:44 PM EDT

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Quoted:
Shhhhhhhhh.

I know that. But in my way of thinking it would have been overgassed running suppressed and I NEEDED to be able to mitigate that because of reasons.
View Quote View All Quotes
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Quoted:



Quoted:

You could have left the stock gas block on and it would run 100%





Shhhhhhhhh.

I know that. But in my way of thinking it would have been overgassed running suppressed and I NEEDED to be able to mitigate that because of reasons.


What's stopping you from putting the stock BCM gas block back on?



Once my can's out of jail it will live on my Kino.  My current plan for dealing with overgassing is to not worry about it and be happy.



 
Link Posted: 4/5/2016 9:14:42 PM EDT
I'm going to try the gemtech bolt carrier for my 10.3" commercial spec DD. It's overgassed, but it runs fine, so I should leave it alone, but "because reasons" I want to try and tune it, but I'm not willing to try an adjustable gas block because I hate unpinned blocks.  Seems like a good compromise and if it sucks I simply swap my old carrier back
Link Posted: 4/5/2016 9:16:08 PM EDT
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Quoted:

What's stopping you from putting the stock BCM gas block back on?

Once my can's out of jail it will live on my Kino.  My current plan for dealing with overgassing is to not worry about it and be happy.
 
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Quoted:
Quoted:
Quoted:
You could have left the stock gas block on and it would run 100%


Shhhhhhhhh.
I know that. But in my way of thinking it would have been overgassed running suppressed and I NEEDED to be able to mitigate that because of reasons.

What's stopping you from putting the stock BCM gas block back on?

Once my can's out of jail it will live on my Kino.  My current plan for dealing with overgassing is to not worry about it and be happy.
 


I wish very badly that I had initially felt the way you feel about this. Now I have a 90 dollar gas block I am just going to use till it breaks then I'll replace it. After this I will NEVER use them again.
Link Posted: 4/5/2016 11:08:46 PM EDT
So did you contact SLR? They have some of the best customer service of anyone
Link Posted: 4/21/2016 8:34:50 PM EDT
I had ADCO cut down a middy DD barrel to 12.5" just for suppressor use. I never expected it to run reliably w/o the can, but it's near 1000 rounds un-suppressed and I've had no problems at all with it.


Link Posted: 4/21/2016 9:36:18 PM EDT
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Quoted:
I had ADCO cut down a middy DD barrel to 12.5" just for suppressor use. I never expected it to run reliably w/o the can, but it's near 1000 rounds un-suppressed and I've had no problems at all with it.
]
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thats because they are ove gased to begin.



had a guy next lane over shooting a new DD.  over gassed like hell.
Link Posted: 4/21/2016 9:48:44 PM EDT
Get a innovative arms war upper.

http://innovativearms.com/war/
Link Posted: 4/21/2016 10:04:46 PM EDT
I feel like this isn't a "BCM 12.5 Kino" Lessons Learned but more a "SLR gas block" Lessons Learned.
Link Posted: 4/22/2016 6:07:28 AM EDT
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Quoted:
Get a innovative arms war upper.

http://innovativearms.com/war/
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^^^This is a good option.  

The Gemtech bolt carrier is good for this scenario too and drops right in.
Link Posted: 4/22/2016 10:41:14 PM EDT
I have three SLR gas blocks, two on SBR's, a 10.5" 5.56 and an 11.5" 6.8 and one on a 16" 6.8 and all get shot a fair bit, almost exclusively suppressed. I have never had an issue. I'd suggest contacting SLR, sounds like you got a dud.

[BTW, I don't bother closing the block when cleaning a rifle, but I do keep the upper right side up since solvents don't drain, run or drip up.]

And just for the "mine runs fine with a standard block" crowd, I'll reiterate that if your rifle runs reliably unsuppressed there is 100% probability it is over gassed when shot suppressed. An over gassed condition can create long term reliability and service life issues, plus there is definitely excessive gas coming into the action making for a dirtier rifle with a more stringent cleaning regimen, and more gas in the face.

JPK
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