The Remington era Parker specification sheets reproduced in
The Parker Story show a 2 5/8-inch chamber for 2 3/4-inch shells.
Remington Specification Sheet GHE, 16-gauge highlighted.jpg
I would think that under Remington ownership they would have gone to chambering the 16-gauge for 2 3/4-inch shells pretty quickly as Remington was the main mover and shaker for the 2 3/4-inch 16-gauge shell when they introduced their Model 11 and The Sportsman autoloaders in 16-gauge in 1931 made for 2 3/4-inch shells.
AUTO EXPRESS New Goods Kleanbore catalog.jpeg
AUTO EXPRESS, #6 Chilled.jpg
When Remington introduced their Model 31 pump in 16-gauge in 1933 it was also made for 2 3/4-inch shells.
Threaded Mode