Something really stinks here.
A bit of background here...
I am a NRA Life Member, a certified firearms instructor, and had my own business one time as a gunsmith.
I am also a Colt certified AR15/M16 armorer. I have been reloading for well over 30 years, to include I-don't-know-how-many tens of thousands of rounds of .223/5.56 ammunition.
During my time in the Army, I was also a Unit Armorer in three separate units, and I can't even count how many cans of M193 ball ammunition I have broken open and emptied (I have the dubious distinction of burning up M16A1's and M60 machineguns, as well.)
Finally, my line of current employment involves gathering evidence, evaluating it, establishing probable cause and effecting lawful arrest. (
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I'll say this: It looks like you were the victim of criminal mischief.
I am familiar with progressive and commercial reloading machines. As long as they are maintained and have a competent hand at the controls, they are almost literally bulletproof. If you are loading .223/5.56 on a commercial reloader (like a Camdex), it is impossible for the machine to feed a bullet of that length without tying up and possibly wrecking the machine.
Thus, you're looking at the probability of someone handloading that round and dropping it in a box, thinking that they were funny.
Look at the "base" of the projectile. I'd be surprised to see any exposed lead--it looks like a solid rod.
I'd like to know how the company got it out--it looks like it has marks consistent with a pattern of rifling. One of the properties of a projectile upon firing is that is is actually swaged under tremendous pressure to a slightly smaller size as it enters the bore. And once it's in there, IT"S IN THERE.
From what I see you were darned lucky. Folks, this is a definite testimony to the strength of the AR pattern rifle. A regular, normal round in that rifle fires at around 52,000 psi. I cannot begin to imagine the horrible temperature and pressure generated when firing that round that blew up your rifle.
I would take the whole mess and find a good lawyer who is experienced in that kind of work. There is a good possibility that there is a nut somewhere who has a grudge against that company, who threw that round into a box.