I think the Browning A5 or the humpback Remington started to arrive on the scene the 1930s but it really wasn't until the 1950s when the Remington 58/(later 1100 in 1963?) and then the Winchester 1400 in 1964???? So apparently it was the 1950s & 1960s when the autoloader shotgun took hold??

Serbus,

Raimey
rse