So, this happened while shooting my newest rifle...five times during one magazine

[m16]

The gun:

1.jpg

It's a BCM 14.5" standard lightweight mid-length barrel, upper is a slick side from JSE Surplus.

The barrel extension has extended feed ramps, the upper does not.

Buffer tube, action spring and H buffer are all BCM, as well as the bolt carrier group.

Here's what happened:

2.jpg

The dents you see are from the lugs on the barrel extension, the rounds were jamming in the upper at an angle.

I should add that this rifle has functioned flawlessly when shooting XM855 and using Magpul/Colt/Okay magazines.

This time, I was using an HK magazine and was shooting Lake City ball ammo.

I should also add that this same magazine and ammo fed fine out of two other rifles on the same day, for some reason this rifle did not like this ammo/magazine combo.

Thoughts?

[MegademiC]

Edit. What did BCM say? Call them first, but if you want to troubleshoot yourself:

Ive seen that from a bent extractor.
Change the bolt, if fixed, put the old one back in but swap extractors with a different rifle. Or lat the extractor on a flat surface. I suspect a bad extractor spring could also cause this.

Could be mags. What I think is happening is that the round being fed is getting loose before or during the feeding process.
In the case a saw, the extractor lost control of the case, it bumped the top round of the mag knocking it loose as the bolt was trying to feed it. The empty case then exited the port.

[rakkasangrunt187]

The gun:

1.jpg

It's a BCM 14.5" standard lightweight mid-length barrel, upper is a slick side from JSE Surplus.

The barrel extension has extended feed ramps, the upper does not.

Buffer tube, action spring and H buffer are all BCM, as well as the bolt carrier group.

Here's what happened:

2.jpg

The dents you see are from the lugs on the barrel extension, the rounds were jamming in the upper at an angle.

I should add that this rifle has functioned flawlessly when shooting XM855 and using Magpul/Colt/Okay magazines.

This time, I was using an HK magazine and was shooting Lake City ball ammo.

I should also add that this same magazine and ammo fed fine out of two other rifles on the same day, for some reason this rifle did not like this ammo/magazine combo.

Thoughts?

Did you use the XM855 on same mag? Some mags just don’t work well with different ammo. For example, one ammo I used did well with standard mag but did not like Magpul or Lancer mags. The problem it seems stems from the feedramp... Something is happening there that may be hitting the bullet in the chamber once it is seated when bolt is racked forward. It could also be the way the bottom of the casing of the particular round that like city ball is using. It might be loose enough to cause a slight angle when bolt is going forward.


Sent from my iPhone using Tapatalk

[MistWolf]

...I suspect a bad extractor spring could also cause this.

Yes. Yes, it does.

...the extractor lost control of the case, it bumped the top round of the mag knocking it loose as the bolt was trying to feed it. The empty case then exited the port.

Typical of an extractor issue, resulting in the damage shown on the cartridge.

[markm]

It's likely the HK junk mag. Is it one of those problematic steel mags?

[m16]

I have not called BCM, figure they will tell me to kick rocks since it's a Frakengun.

The HK magazine is definitely steel and the follower is metal, not sure if it's one with a known issue but if it is I'm throwing it in the trash.

This did not happen when using PMAG's or aluminum USGI's.

As for the extractor being bent, not really sure how to check it since only the sides have level surfaces...

3.jpg

[AndyLate]

Sample of one, but my HK steel mag is problematic. I would try any of the mags you mentioned and the ammo you had an issue with.

[GH41]

Sell the HK magazine. Take the 30 bucks and buy 3 Okay aluminum magazines. It's probably not contributing to the issue but I would feel better with the M4 ramp cuts in the receiver. It isn't difficult or expensive to do.

[MegademiC]

I didnt know HK mags had a rep, I thought they were all good.
Absolutely could be a mag issue(mechanically). Mark the mag, keep shooting, track malfunctions, and if its always that mag, trash it.

[CoryCop25]

HK rifle mags are great for propping my garage door open.