Formerly reliable BCM 11.5" upper has sudden issues PART II

**1911-A1** · 12-18-18, 18:15

Thanks to everyone's advice I fixed the cycling issues I was having by replacing the gas tube, as the carrier end had worn smooth and was no longer sealing properly on the gas key.

https://www.m4carbine.net/showthread.php?210796-Formerly-reliable-BCM-11-5-quot-upper-has-sudden-cycling-issues

HOWEVER,

My upper has now decided to have doublefeed malfs. Several per mag. Magazine choice doesn't matter.

I swapped the BCM BCG out with the PSA $60 BCG that was recently on sale, and the doublefeeds stopped. The recoil with the PSA unit is MUCH sharper than the BCM, but I can't see any noticeable difference between the two BCGs. I'm assuming the extractor needs to be replaced or adjusted, but I can't figure out why the recoil is so much different between the two. Am I losing gas somewhere with the BCM?

**MistWolf** · 12-18-18, 19:10

Are you talking about true double feed, where two live rounds are jammed in the action? If it's a true double feed, it's your magazine.

Or are you talking about an empty and a live round jamming the action? If it's an empty and a live round jamming your action, you have a problem with your extractor, most likely the spring.

Why did it show up after fixing your gas leak? Because the extra carrier speed is placing more strain on the extractor. With the added strain, the extractor is losing control of the extracted case before it can be ejected.

**26 Inf** · 12-18-18, 19:24

I'll go a little further on Mist Wolf's explanation and add that the reason the PSA's BCG recoil is much sharper, and it extracts whereas the BCM BCG does not is due to not only a fresh extractor and spring on the PSA, but a better gas seal elsewhere, probably in the gas rings. You also might want to check the ejector on the BCM bolt.

Should be a relatively easy fix, and you have two good BCG's:

https://www.bravocompanyusa.com/BCM-...d-bolt-kit.htm (no ejector parts)

https://palmettostatearmory.com/bolt...epair-kit.html (contains ejector, ejector spring and ejector roll pin)

**Iraqgunz** · 12-18-18, 19:56

As Mist stated, we need to determine if this is a "double feed" or a failure to extract and then a failure to feed. I would be looking specifically at the extractor spring first.

**1911-A1** · 12-18-18, 21:15

Thanks again for the help!

That's an important distinction, as the malfunction was not a true doublefeed, as mentioned above and I should have made that more clear, apologies. One case was empty and didn't clear the feed path of the next round. Had it been a true DF I'd have looked at the mags instead of the BCGs.

I have a spare parts kit, so I'll swap out the spring in the BCM and see what happens. I was mostly confused about the difference in recoil, and I think that distracted me from troubleshooting properly.

This has been my main training/carbine class rifle so it's got some mileage on it, and I'm starting to see parts failure.

**markm** · 12-18-18, 22:29

Wouldn't we be looking at a possible EJECTOR spring issue as opposed to the extractor?? Either of these are easy to quickly assess. With the bolt out of the gun, does an empty piece of brass "fling" off the bolt face when hooked under the extractor??

**prepare** · 12-18-18, 22:52

The 11.5's will wear stuff out quicker than a 14.5 or 16. More gas port erosion, gas ring/tube wear. The bolt takes more of a beating too if the gun is overpassed.

**Iraqgunz** · 12-18-18, 23:33

For sure, which is why it's important for people to actually articulate the issue. This would be fairly easy to troubleshoot. Personally I would approach it from a one-at-a-time method and replace the extractor spring first and then the ejector. This way you nail it down exactly and have a reference for the next malfunction.

Originally Posted by markm

Wouldn't we be looking at a possible EJECTOR spring issue as opposed to the extractor?? Either of these are easy to quickly assess. With the bolt out of the gun, does an empty piece of brass "fling" off the bolt face when hooked under the extractor??