When I was a boy, in Oklahoma, a long time ago, many of my friends fathers had old sawed off 12 gauges left over from their fathers times. They were used mostly for hunting in blackjak thickets, not criminal or militia use. My guess is that when they were restricted they were probably mostly hunting weapons. I'd be willing to venture that most of them never got registered either.
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Shotguns were sawed into pistols to use against snakes.