Posted: 1/6/2017 12:20:15 AM EDT
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I have been in discussion with someone about the fact that BCM does not pin their gas blocks, and that they claim it negated BCM from being suitable for hard use.
I do not agree with this based on what I have read about the way BCM gas blocks are installed... But I want to confirm my info if possible. I read much of this at varying points in the past, and can no longer find the sources directly. I am hoping I can get info here. (I know some models BCM makes, do have pinned blocks, I am only referring to ones that are not pinned) From my understanding... The barrels are dimpled for proper alignment, and to help prevent slipping. The gas blocks have a slight press fit to the barrel. That "green loctite" is used in between the block and barrel. That the set screws are torqued tight and have high temp, high strength loctite threadlocker applied. An aside on the "green loctite" mentioned above. I have assumed it was loctite "retaining compound" as the green low strength threadlocker seemed to not be appropriate for such use. "Retaining compound" is designed to hold metal parts together, especially ones that are slid onto a round shaft, like bearings. (or a gas block on a barrel in this case) Basically it is a high strength metal adhesive. Shear strength is around 3800psi for the "green" version. I have used this stuff, and it is extremely difficult to remove parts without lots of heat. If this method is in fact the method used... I am more than confident the gas block will not fail during use, its basically bomb proof. It may not be pinned, but if not "as good", is at least... almost as good. And I have never heard any account of a BCM factory installed gas block failing. If anyone has any insight into how they are installed, I would be grateful. |
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I'm not aware of any retaining compound being used on the low profile gas blocks themselves. I do know that the set screws will actually bite into the barrel metal enough that there's no way they'll slide and IIRC they use high temp loctite on the screws to make sure they don't back out. It's not going anywhere.
Previously I was wary of unpinned gas blocks but I've never seen one come loose on a factory BCM upper. |
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Quoted:
I'm not aware of any retaining compound being used on the low profile gas blocks themselves. I do know that the set screws will actually bite into the barrel metal enough that there's no way they'll slide and IIRC they use high temp loctite on the screws to make sure they don't back out. It's not going anywhere. Previously I was wary of unpinned gas blocks but I've never seen one come loose on a factory BCM upper. |
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Quoted:
My gas block is loose on my bcm upper. Â I ran it through 2 carbine classes over the past couple year and put maybe 3-5k rounds through this upper. Â I just noticed it recently - there is about an 1/8" gap between the gas block and the barrel. If you have a 1/8" gap, I highly doubt your rifle would be cycling at all, it would most definitely be short stroking. |