Help with ugly FTE

[t15]

I'm guessing you just swapped BCG's and not just the bolts.

Swap the bolts into the other BCG and see if the malfunctions still occur. Think about this and see if it makes any sense - FTE's are sometimes caused by the weapon beginning to cycle before the case has contracted after firing - over gassed. If one bolt doesn't seal as tight in the BCG (worn gas rings) then it might let the weapon function because of a slight delay/less abruptness in cycling. So my theory is the new BCG is tighter and that combination, combined with the shorter gas system on the 11.5 is causing the FTE's.

Also check the carrier keys to see if you have any signs of gas leakage - 'v' shaped carbons jets.

Hey it's one o'clock, the only reason I'm up is because my daughters completely hosed up the tub and toilet in their bathroom. Girls.

OK, I did as you suggested and swapped the troubled BCM bolt into the DD carrier and the DD bolt into the BCM carrier. With the BCM bolt in DD carrier, the first magazine was slow going, failures every 2 rounds or so. After the first 20, I was able to get through 2 more mags without any failures! The DD bolt in BCM carrier gave me 0 failures through the first mag.

Today I used only Federal XM193 and did a few runs with the bore snake. Otherwise, nothings changed. Before swapping bolts, I did try a new gen2 30 pmag-which didn't help. When I switched back to BCM bolt and carrier, the issue came back. It may have been wishful thinking, but it did seem better. Here are some pictures (actually mine this time). Thanks to everyone for taking the time to look!


Here is how it looks after the first round goes bang and trigger fails to reset.
resize1.jpg

Here are the fired and unfired rounds from the first picture. The dents were not present before shooting.
resize2.jpg

This is the same fired case from the first 2 pictures.
resize3.jpg

Another common look, different from first photo.
resize4.jpg

I loaded 5 total rounds, 1 at a time in the magazine. (2 of 5 ejected) In this picture pointing the muzzle up resulted in the casing falling out free.
resize5.jpg

[notorious_ar15]

I will defer to the more experienced members on here; however, I wanted to add my experience - when I had intermittent issues with double feeds, it turned out to be the ejector spring. The problem would usually start to crop up once the rifle started to warm up from shooting.

[TacMedic556]

Strong work. I wish I could see the picture you posted on my device. It's blank.

[t15]

Thanks guys, I am going to try a few more easy things and call BCM before replacing any parts. Here's one more picture from the single round in the mag drill.

resize6.jpg

Still had a fun day at the range, amazing weather!

resize7.jpg

[MegademiC]

Sounds like ejector or extractor issues. My bro had almost identical problem due to an outward-bent extractor. Call BCM. I'm sure they'll fix you up.

I'd find out why (for curiosity) then send it back.

[Caduceus]

Gas tube leaking? Far enough to push the BCG back not not enough to clear the round?

Though improvement with different bolts seems to argue against this.

[BufordTJustice]

Gas tube leaking? Far enough to push the BCG back not not enough to clear the round?

Though improvement with different bolts seems to argue against this.

Extractor spring or gas rings allowing too much leakage.

Either way, BCM will get the OP squared away in a hurry.

[Clint]

Yes, looks like an extractor issue.

A replacement bolt should take care of things.

[MistWolf]

The rifle may have a failure to extract/eject problem, however, it is definitely short stroking

Here is how it looks after the first round goes bang and trigger fails to reset.
resize1.jpg

That is clearly the result of the BCG failing to travel fully to the rear

[Shiz]

That is clearly the result of the BCG failing to travel fully to the rear

To me it looks like the bolt went back far enough to grab another round. Just looks like it let go of the spent shell too soon. I am good at being wrong though.