Yes, American pumps such as M12 and 870, along with Browning A5's were common on North American trap and skeet fields fields in the 30's through the 1960's and many championships were won with them. They were common because they were affordable and they were competitive against others of this type. However, the Browning Superposed was the only decent over/under at this time, Perazzi, Beretta, Kreighoff, and most other top competition guns had not yet made their mark, and it was too expensive for many shooters however it paved the way for over/unders by showing advantages that took more than their share of top tier wins. Once the competitive advantage of the best over/unders was clearly demonstrated and understood they quickly took over as competition guns. It is a novelty today to see a pump or two or even more than a handfull of autos at a major competition like a provincial/ state Grand with hundreds of competitors. The reason being that these shooters all want to win and they use the tools that they believe gives them the best opportunity to do this. Yes, any gun can and eventually will break, but one that lets you down in a major tournament where every target is vital will be quickly replaced.