I had a partial case head separation using a 1.8oz buffer

[LRRPF52]

I don't dispute this. But it is irrelevant to my failure models. What I need to see is this type of data during an actual failure. One similar to OPs would be great. What you are sharing is what happens under normal conditions. That curve will be much different for an in battery case rupture. At the beginning it would look fine. T = 0. And for sure any in-battery case rupture is going to occur between T = 0 and T at peak. And if it happens before T at peak, then it will immediately drop below that point after that.


Agreed. The failure node in the brass was at the bend point as it bent to the shape of the feed cone. This was at the extractor location too, where the brass had literally more volume to expand into.



To be clear, there are two areas only. The rupture point and the mouth of the case. The gas will escape only those two points and the one that happened first will have more gas escape that way.


When this happens the damage will depend on the pressure that causes the failure like I already explained. You are again assuming the amount of damage dictates one particular failure. That's an assumption but it's possible to just have a blowout in battery with only enough residual pressure to blow out the magazine. Again, each failure case needs to be analyzed individually. there will be similarities AND differences in all of them.


With all this you are assuming the pressure follows this curve after the rupture. It will unequivocally have a totally different pressure curve once the rupture occurs. See my first points above.



All this is simply explained by an in-battery case head that is ballooning into the unsupported area of the feed cone and also into the area of the extractor due to the smaller volume of the extractor relative to the lugs.

That's exactly what I see. Again. And goodnight for now!

Nope. If the case fails prior to pmax, you still have considerable amounts of powder that has not been converted, and now you just provided a very tiny aperture for it to continue its burn through.

The powder burn wouldn’t magically stop once the case ruptured in the imaginary event you’re describing.

It would continue to be converted in that tight space formed by the case in-battery, the bolt face, barrel extension, which is why you see in-battery failures turn AR-15s into grenade-like devices.

Remember that the projectile would still be static or in a retarded start-pressure position in this model, obstructing the bore now that a new point of relief has been found.

This is why bolts, barrel extensions, carriers, and upper receivers turn into fragments with an in-battery catastrophic failure.

The tightness of the space doesn’t allow clean, well-guided venting of the continued burning propellant.

In the OP’s demonstrated failure, there is no soot residue emanating from the failure point, which means that the propellant was already converted.

If you have ever seen in-battery failures, there is a ton of soot around the chamber and remaining parts fragments.

His brass is squeaky clean, with a very coherent failure node aligned perfectly with the extractor.

The fact he was using a 1.8oz buffer should put all of this to rest.

That is early unlocking all day long, a literal recipe for it.