My senior year in high school I had an internship with a company in Roseville Michigan that was a early NDI company (NDI non destructible testing). I was doing maga-flux testing on M-16 bolts (the item name on the work order). I was to determine if the bolts had cracks in them. About 20% of the bolts were rejected due cracks at the face of the bolts. These bolts were delivered almost daily 500 bolts at a time. This was in 1966. In December 1967 I was in Viet Nam carrying the weapon I had inspected. The weapon had a three pronged flash hider we also used to open c-rat cases. This same weapon would jam, or fail to fire quite often. I oped for a 12 Gage shotgun and a 1911. I have no idea what company was sending the material for testing.

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Carpriver.