Tinker,
Earlier than that, I believe reading about a shipment of Mexican produced concrete reinforcement rod that set detectors off as it passed on truck near the White Sands military installation.

It was really, really hot.

Maybe should mention at this point that I'm OK with good old steel barrels. Hell, my Darne 12 weighs six ozs less (6lbs even, to be exact) than my 16, and isn't what I would use for 100 targets any day of the week. Either gun, come to think of it.
Best,
Ted