Can a magazine cause failures to *eject*?

**Circle_10** · 05-13-17, 05:45

I was shooting my carbine, a retro build, off a rest the other day and was getting these same malfunctions over and over.

When I got the first one I briefly thought it was a regular double feed, however upon clearing it, it turned out the top casing each time was a spent one that failed to eject, with the lower round being a live cartridge trying to feed into the chamber.
One thing I noted was that it only happened with one specific Okay brand 20-rounder when I was firing it slowly off a rest. Cycled fine when fired offhand with a couple Okay 30s both slow-ish and as fast as I could. I also loaded up and fired the problem 20 rounder offhand without issue.
At home I checked the gas key, ejector, extractor and gas rings and all seemed fine.
Went back out with the carbine two days later and although the weather kept the firing session short I tried shooting off the rest with a few different mags and once again had the failures to eject with the same mag and no issues with the others. Most of the FTEs looked more or less identical to the ones the previous day, with a couple that were more like stovepipe malfs where the case head had made it out if the ejection port, but the neck was being held in by the bolt, with a live round trying to feed into the chamber as usual. This time the malfs only happened during the first half of the mag.

My first inclination would be to blame the mag however I didn't think failures to eject were generally attributable to bad mags. The mag was probably getting pressure exerted on it when I was shooting off the rest but I'd always heard that unless something is out of spec that shouldn't cause a malfunction. And even then I'd think it would be more of a straight-up failure to *feed*.
The best theory I could come up with so far is that the mag is ever so slightly out of spec, and generally not enough to cause an issue firing off hand, but the pressure exerted from shooting off the rest is pushing it up or causing it to shift just enough that the BCG is dragging on it when cycling.

Anyone have any better ideas? The gun is my first assembled-from-scratch AR so the notion that I might have something incorrectly during the process is nagging at me.

Gun specs as follows if it's relevant: Brownells A1 upper, 14.5" BCM barrel, carbine gas length, BCM bolt carrier group, currently on a placeholder Stag lower until I get a proper A1 style, the Colt receiver extension has an "H" buffer in it.

Ammo was from a batch of Prvi Partizan M193 with an '07 headstamp.

**MegademiC** · 05-13-17, 08:00

My theory:
If the round pops out of the mag, it could knock the spent case out of the extractor. It looks like the extractor is losing the case towards the end of the cycle.

I'd toss that mag, could have gotten damaged.

**Circle_10** · 05-13-17, 08:26

I'll look over the extractor again, maybe there is a problem with it and it was just coincidental that it was the same mag, because now that I think about it I don't recall seeing any marks on the mag to suggest the BCG was dragging on it.

**26 Inf** · 05-13-17, 10:12

There have been a couple threads recently which indicate that you probably need to get the upgraded extractor spring set from BCM. I have a BCM BCG and it has run without a hiccup, but others have experienced otherwise.

**Circle_10** · 05-13-17, 13:02

Why just recently? Has something changed with BCM's BCGs? I thought they shipped with the proper extractor spring in them already (Black polymer insert, five coil spring, isn't it?) currently I have BCM BCGs in every complete AR that I own, I also have the O-Rings they ship with the BCGs as an extra in my parts bin but never felt like I needed to install them.
At least if it is an extractor issue that should be a fairly easy fix.

**JC5188** · 05-13-17, 14:03

Originally Posted by Circle_10

Why just recently? Has something changed with BCM's BCGs? I thought they shipped with the proper extractor spring in them already (Black polymer insert, five coil spring, isn't it?) currently I have BCM BCGs in every complete AR that I own, I also have the O-Rings they ship with the BCGs as an extra in my parts bin but never felt like I needed to install them.
At least if it is an extractor issue that should be a fairly easy fix.

What 26Inf said.

No manufacturer is immune to occasional hiccups. Could be tolerance stacking, process changes, etc. Who knows?

How each manufacturer handles problems that arise is a different story.

Sent from my iPhone using Tapatalk

**Circle_10** · 05-13-17, 15:55

I interpreted his comment as suggesting there was some known issue surfacing with BCM BCGs of late beyond the normal occasional QC hiccups that every manufacturer runs into now and again.
Of course, I suppose my FTE issue might not even be the extractor but it's at least something else for me to check and makes sense. Luckily I've already got the parts kicking around if that is the case.

**26 Inf** · 05-13-17, 19:52

Originally Posted by Circle_10

I interpreted his comment as suggesting there was some known issue surfacing with BCM BCGs of late beyond the normal occasional QC hiccups that every manufacturer runs into now and again.
Of course, I suppose my FTE issue might not even be the extractor but it's at least something else for me to check and makes sense. Luckily I've already got the parts kicking around if that is the case.

Here is the most recent one that I recall: https://www.m4carbine.net/showthread...ure-to-extract

I do not know whether they ship all bolts with the enhanced springs or not. I've never had problems with mine, maybe because it is on a rifle length system with an A5 tube and buffer.

That is all, didn't mean anything yah, or nay.

**Kdubya** · 05-13-17, 20:33

Originally Posted by 26 Inf

Here is the most recent one that I recall: https://www.m4carbine.net/showthread...ure-to-extract

I do not know whether they ship all bolts with the enhanced springs or not. I've never had problems with mine, maybe because it is on a rifle length system with an A5 tube and buffer.

That is all, didn't mean anything yah, or nay.

I think this does make like 4-5 somewhat recent threads with similar issues; with a common denominator being BCM BCGs. Here's a couple others I was able to find.

https://www.m4carbine.net/showthread...(eject)-please

https://www.m4carbine.net/showthread...raction-issues

A couple individuals in those threads did state that their BCGs from BCM didn't come with the enhanced springs/hardware. Swapping the springs is easy, quick and cheap. It may not be the issue, but it's probably a good place to start.

**JC5188** · 05-13-17, 20:50

Originally Posted by 26 Inf

Here is the most recent one that I recall: https://www.m4carbine.net/showthread...ure-to-extract

I do not know whether they ship all bolts with the enhanced springs or not. I've never had problems with mine, maybe because it is on a rifle length system with an A5 tube and buffer.

That is all, didn't mean anything yah, or nay.

That's is what I meant, I knew you were pointing to the recent issues.

Originally Posted by Circle_10

I interpreted his comment as suggesting there was some known issue surfacing with BCM BCGs of late beyond the normal occasional QC hiccups that every manufacturer runs into now and again.
Of course, I suppose my FTE issue might not even be the extractor but it's at least something else for me to check and makes sense. Luckily I've already got the parts kicking around if that is the case.

The second part of my post was to your question of "why just recently?" Good manufacturers will sometimes have small isolated issues...usually in the same place, or with the same part.

When manufacturers have multiple issues, with multiple parts...that's a sign of a poor process(es).

Sorry for the confusion.

Sent from my iPhone using Tapatalk

Thread: Can a magazine cause failures to eject?

Thread Tools

Display