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Posted: 3/14/2021 10:16:33 PM EDT
UPDATE: Ended up sending the upper back to BCM and they returned it with a new BCG. All is well now.
My son has an 11.5" BCM upper, complete with their BCG. It has been running fine for approximately 5K rounds until once in a while it won't eject. He swapped out the BCG and it seems to be running again. I took pics of the BCG around the gas key and it looks like it is leaking there. Thoughts?  Attached File Attached File |
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Posted: 3/14/2021 10:28:48 PM EDT
[#1]
Sure does look like it.
What is up with BCM QC? Their quality has went to shit. I don't even consider them Tier 2 anymore. |
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Posted: 3/14/2021 10:41:56 PM EDT
[#2]
It does look like it's leaky.
Might want to try replacing the extractor spring and o-ring also. Mine wore out and had ejection issues starting prior to replacing. |
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Posted: 3/15/2021 1:00:36 AM EDT
[#3]
Looks like it. One of the screws could be broken. Turn on the screws and see if they move. Torque should be 58 in/lbs.
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Posted: 3/15/2021 1:15:06 AM EDT
[#4]
This typical BCM as of late.
Ive seen a similar issue with a friends rifle. |
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Posted: 3/15/2021 4:27:40 AM EDT
[#5]
Quote HistoryQuoted: Looks like it. One of the screws could be broken. Turn on the screws and see if they move. Torque should be 58 in/lbs. 37 in lbs, since the newer torque requires the newer stronger allen bolts, and stronger Key metals that sometimes are not found on the civilian rifle parts. So mil spec parts from say Colt or FN military armory bins since these parts have been spot lot checked at least three times before you put your hand on them , yes on the 58inlbs. Anything else, use the old 37inlbs since it a spec that has been tested time and time again to work with pretty much any AR keys and bolts. |
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Posted: 3/15/2021 12:34:53 PM EDT
[#6]
The seating torque on three different manufacturers web site for 1960 series alloy steel 8-32 socket head cap screw appeared to show the seating torque between 55 in pounds and 59 inch pounds depending on the manufacturer. The only "magic" I know of in a mil spec carrier key screw is the knurling requirement.
https://www.stanleyengineeredfastening.com/-/media/web/sef/resources/docs/other/socket_screw_tech_manual_1.ashx pg 18 catalog pg https://www.holo-krome.com/uploads/7/2/7/5/72754089/hk_consolidated_tech_manual_full_2015.pdf pg 32 catalog pg https://www.unbrakousa.com/images/pdf/engguide.pdf pg 7 catalog pg |
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Posted: 5/25/2021 9:03:24 AM EDT
[#7]
Quote HistoryQuoted: Looks like it. One of the screws could be broken. Turn on the screws and see if they move. Torque should be 58 in/lbs. We tried to put some torque on the screws but they did not budge, in either direction. Ended up sending the upper back to BCM and they returned it with a new BCG. All is well now. |
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