You also describe the results of an out-of-battery fire and/or immediate barrel obstruction. All other things being equal, you could have literally
filled the case under the bullet with H335 (29gr) and only generated 70,000 psi -- unlikely to have blown up the rifle as depicted.
See...
http://www.youtube.com/watch?v=Oh1ly...layer_embedded
for classic example.
I realize that the AR bolt/carrier design is such that the bolt
must have rotated long before the firing pin can protrude. (Pull the bolt/carrier group out and try it, you'll see.) But I have also seen an instance of what you see in the video, and an instance wherein the bolt was opening too fast (with high-pressure gas expanding the exposed case head portion just ahead of the web like a balloon.)
Anything you can think of that would have hindered action lock-up?
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post: Be sure your wife (God bless her) knows she is now a member of a very exclusive survivors club, and that
no one on the cocktail circuit can likely match her small talk topic.
