I didn't actually own a 16 back in those days either. I did know several "Bird" hunters who shot the old Browning Sweet 16s & some of them were chambered for the short shell. They had no problems finding shells in this part of TN My guess would be the majority of the 2 9/16: shells went either to the southern Bird hunters or New England grouse & woodcock hunters. These were where the 16 gauge truly was appreciated.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra