Help me troubleshoot FTE (eject) please

[websniper]

Newly built upper. All new parts on upper

AP upper receiver
Ballistic Advantage Hanson 16" bbl and lo pro gas block (pre-drilled for pin)
BCM BCG (O-ring not installed)
BCM gas tube (mid) and pin

Lower is known to function correctly
BCM RE, spring, and H buffer
CMMG parts kit / trigger

Magpul Gen 2 Pmag x 2 known working

Wolf Gold

I'm getting a few failures to eject properly on my new upper build up. I slapped the upper on this lower I have that normally has a BCM factory mid-length light weight upper riding on it that functions 100% just to take to the range and function test. Needless to say, it didn't go great.

I loaded a few single rounds and fired them and it locked back every time. Loaded a few with 2 round and fired those and they locked back. Loaded 3 and got this failure.

IMG_0772[1].jpg

Another angle
IMG_0773[1].jpg

Loaded a few more triples and they fired ok. Loaded 10 (still Wolf Gold) and had another same type of failure partway through the mag.

IMG_0778[1].jpg

At this point, I was out of Wolf. Brass from Wolf Gold was kind of stringing out in a pattern from 2:30 to roughly 3:30.

Loaded 60 rounds in 2 30 round mags of Federal XM193 and blew through all of those without fail.

Is this a gas issue? Did I perhaps bork the gas block install? Or is it an extractor issue? I'm thinking about installing the o-ring and giving it another go...

Suggestions welcomed. This is supposed to be my new "go-to" upper and I'm already doubting it... I don't like failures and tend to ditch them for gear that runs. But since this wasn't a factory upper and built by me, I'm quite positive there may be something done incorrectly that's easily resolved.

[Clint]

If it locks back with singles, there is enough gas.

If this is a brand new BCG, this particular unit hasn't been prooven good.

I'd look at the extractor/ejector.

Try swapping in the BCG from the 100% working factory upper to help isolate the issue.

[MegademiC]

Looks like extractor/ejector issues to me as well.

How does the ejector feel? Is it difficult to depress?
Does the extractor extend inside circle formed by the bolt face cutout for the rim? If depressed, does it spring back?

Swap the bolt with a known good one and see what happens.

[websniper]

Took it back out with a known good BCG from a factory BCM upper. Ran singles and a few triples then a few full mags. All good. When I yanked the new BCG out and compared it to the working BCG, the only thing I'd say is notable is that the extractor takes noticeably less pressure to move than the "good" BCG.

Should I fire off an email to BCM or just slap the o-ring in there and go back out and test it? FWIW, the working BCG doesn't have the 0-ring installed either.

That all being said, I put the new BCG back in and ran about 70 rounds through it without a malf. However, the empties flew significantly less distance from where I was shooting than with the known good bolt.

[Kdubya]

There was another thread similar to this a month or so back; FTEs and double feeds, and he was also running a BCM BCG. It was mentioned by one member that there were other recent reports of BCM bcgs malfunctioning. He stated that in every instance the issues went away after replacing the extractor and/or ejector springs. So, maybe a batch of their BCGs made it out with some bad springs. The whole thread (linked directly to the spring replacement portion) can be found here.

Starting with the ejector and extractor is an easy and inexpensive place to start. Trying the o-ring isn't a bad idea. However, if you subscribe to the "o-rings are a bandaid for inferior springs", that means you'll want to replace the spring anyways; if the o-ring "fix" works.

[Iraqgunz]

I would contact BCM and let them address the issue.

[MistWolf]

It's the extractor spring. Install a Colt extractor spring

[Locutus]

It's the extractor spring. Install a Colt extractor spring

I'm curious why you say that since the case has clearly been extracted. Ejection appears to be the problem.

[26 Inf]

Locutus:

I think you'll get his frame of reference from this thread: https://www.m4carbine.net/showthread...raction-issues

Also from post #4 by the OP: When I yanked the new BCG out and compared it to the working BCG, the only thing I'd say is notable is that the extractor takes noticeably less pressure to move than the "good" BCG.

The theory was that the extractor was losing control of the round before full extraction occurred.

I do agree with you, generally when you see that 'v' doublefeed with an empty case on top it is an ejection issue, but apparently this has happened before with a batch of BCM bolts.

[Locutus]

Locutus:

I think you'll get his frame of reference from this thread: https://www.m4carbine.net/showthread...raction-issues

Also from post #4 by the OP: When I yanked the new BCG out and compared it to the working BCG, the only thing I'd say is notable is that the extractor takes noticeably less pressure to move than the "good" BCG.

The theory was that the extractor was losing control of the round before full extraction occurred.

I do agree with you, generally when you see that 'v' doublefeed with an empty case on top it is an ejection issue, but apparently this has happened before with a batch of BCM bolts.

Good info - Thank you!


mark5pt56, I got your message and thank you too!