My boss helped some guys test the Masterlock claim back in the late 1970s. They only brought along .22s, .30-30s and 12 gauges, he supplied the .30-06, the M14 and the Gyrojet (he had been plinking at the range when they showed up). The last one was the most impressive, it took about 10 shots to hit it, but when it did, that sucker exploded.
Kharn