AR15 - Catastrophic Jam

[alwie]

Im not sure what to even label my failure on the range today, so I am calling it a ‘catastrophic’ jam till someone corrects me! Further, this was due to my carelessness, I think.

I was doing load development this week and was on the range today again. My load was over press by quite a bit …. see attachment #1

My gas system was very much overgassed. To the point where my cases were being dented at the mouth by the brass defector …. see #3 attachment.

The result was a case jammed that I could not get to extract at the range and had to take my AR apart to finally get the spent case out of the chamber …. see attachment #2. Does the case remind you of other images of  6mm ARC cases people have posted?

I think that the banding we have seen occasionally is due to overgassed ARs with a hot load. The over gassing causes the case to start extracting too soon. What do you think?

[grayfox]

The "magnum band" at the bottom comes from gas pressure from the too-hot of a load. The case is not moving at that time but that overpressure happens while it is still in lock up. That bottom portion is not supported by the chamber, so is able to expand.

[alwie]

The "magnum band" at the bottom comes from gas pressure from the too-hot of a load.  The case is not moving at that time but that overpressure happens while it is still in lock up.  That bottom portion is not supported by the chamber, so is able to expand.

Okay, good to get the exact mechanism. Thx

[StoneHendge]

That's not catastrophic until the case head gets ripped off and the rest of the case gets stuck in the chamber 

[alwie]

That's not catastrophic until the case head gets ripped off and the rest of the case gets stuck in the chamber 

I stand corrected and hope my case head never gets ripped off!

[SpeyRod]

In my LT creedmoor I started getting indications of case head failure with a known load in that gun. I didn’t heed the warning and wound up getting a ch separation. It was exciting to say the least. I did some research and realized I messed up and put a lighter buffer in after cleaning. The Hornady cases were also on firing #4. Lesson learned and it only cost me a $70 magazine. Gun was fine.

Definitely back off on that charge. Make sure you aren’t using bolt gun data.